diff --git a/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Design/TemplateEdit.razor b/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Design/TemplateEdit.razor
index 76ac00d0..6897e66e 100644
--- a/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Design/TemplateEdit.razor
+++ b/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Design/TemplateEdit.razor
@@ -4,6 +4,7 @@
 @using ZB.MOM.WW.ScadaBridge.Commons.Entities.Templates
 @using ZB.MOM.WW.ScadaBridge.Commons.Entities.Sites
 @using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories
+@using ZB.MOM.WW.ScadaBridge.Commons.Types
 @using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums
 @using ZB.MOM.WW.ScadaBridge.TemplateEngine
 @using ZB.MOM.WW.ScadaBridge.TemplateEngine.Services
@@ -80,6 +81,10 @@
     private string _attrName = string.Empty;
     private string? _attrValue;
     private DataType _attrDataType;
+    // List-attribute authoring state (DataType.List only): the element scalar
+    // type + the per-element string rows. Encoded to canonical JSON on submit.
+    private DataType _attrElementDataType = DataType.String;
+    private List<string> _attrListRows = new();
     private bool _attrIsLocked;
     private string? _attrDataSourceRef;
     private string? _attrFormError;
@@ -553,17 +558,32 @@
                                 </div>
                                 <div class="col-12">
                                     <label class="form-label">Data Type</label>
-                                    <select class="form-select" @bind="_attrDataType">
+                                    <select class="form-select" value="@_attrDataType" @onchange="OnAttrDataTypeChanged" disabled="@editing">
                                         @foreach (var dt in Enum.GetValues<DataType>())
                                         {
                                             <option value="@dt">@dt</option>
                                         }
                                     </select>
+                                    @if (editing)
+                                    {
+                                        <div class="form-text">Data type is fixed once the attribute is created.</div>
+                                    }
                                 </div>
-                                <div class="col-12">
-                                    <label class="form-label">Value</label>
-                                    <input type="text" class="form-control" @bind="_attrValue" />
-                                </div>
+                                @if (_attrDataType == DataType.List)
+                                {
+                                    <div class="col-12">
+                                        <AttributeListEditor @bind-ElementDataType="_attrElementDataType"
+                                                             @bind-Rows="_attrListRows"
+                                                             ShowElementType="@(!editing)" />
+                                    </div>
+                                }
+                                else
+                                {
+                                    <div class="col-12">
+                                        <label class="form-label">Value</label>
+                                        <input type="text" class="form-control" @bind="_attrValue" />
+                                    </div>
+                                }
                                 <div class="col-12">
                                     <label class="form-label">Data Source Ref</label>
                                     <input type="text" class="form-control" @bind="_attrDataSourceRef" placeholder="Tag path" />
@@ -1535,6 +1555,8 @@
         _attrName = string.Empty;
         _attrValue = null;
         _attrDataType = default;
+        _attrElementDataType = DataType.String;
+        _attrListRows = new();
         _attrIsLocked = false;
         _attrDataSourceRef = null;
     }
@@ -1547,6 +1569,8 @@
         _attrName = attr.Name;
         _attrValue = attr.Value;
         _attrDataType = attr.DataType;
+        _attrElementDataType = attr.ElementDataType ?? DataType.String;
+        _attrListRows = DecodeListRows(attr.Value, attr.ElementDataType);
         _attrIsLocked = attr.IsLocked;
         _attrDataSourceRef = attr.DataSourceReference;
     }
@@ -1558,12 +1582,72 @@
         _attrFormError = null;
     }
 
+    // Switching the data type clears stale list state so a List ⇄ scalar
+    // toggle never carries the other mode's value into the submit.
+    private void OnAttrDataTypeChanged(ChangeEventArgs e)
+    {
+        if (!Enum.TryParse<DataType>((string?)e.Value, out var dt) || dt == _attrDataType) return;
+        _attrDataType = dt;
+        if (dt == DataType.List)
+        {
+            _attrValue = null;
+            if (_attrListRows.Count == 0) _attrListRows = new();
+            if (!AttributeValueCodec.IsValidElementType(_attrElementDataType))
+                _attrElementDataType = DataType.String;
+        }
+        else
+        {
+            _attrListRows = new();
+        }
+    }
+
+    // Decodes a stored List JSON value into editable string rows. A malformed
+    // stored value (e.g. hand-edited / element-type mismatch) is shown as empty
+    // rather than crashing the editor — the user can rebuild it.
+    private List<string> DecodeListRows(string? value, DataType? elementType)
+    {
+        if (string.IsNullOrEmpty(value)) return new();
+        try
+        {
+            var decoded = AttributeValueCodec.Decode(value, DataType.List, elementType ?? DataType.String);
+            if (decoded is System.Collections.IEnumerable items)
+                return items.Cast<object?>()
+                            .Select(x => AttributeValueCodec.Encode(x) ?? string.Empty)
+                            .ToList();
+        }
+        catch (FormatException)
+        {
+            // Malformed stored value — start from empty so the editor still opens.
+        }
+        return new();
+    }
+
     private async Task SaveAttribute()
     {
         if (_selectedTemplate == null) return;
         _attrFormError = null;
         if (string.IsNullOrWhiteSpace(_attrName)) { _attrFormError = "Name is required."; return; }
 
+        // Resolve the value + element type per data type. List attributes encode
+        // their rows to canonical JSON and validate them locally before submit
+        // (TemplateService persists directly and does not list-validate).
+        string? attrValue;
+        DataType? elementType;
+        if (_attrDataType == DataType.List)
+        {
+            elementType = _attrElementDataType;
+            attrValue = AttributeValueCodec.Encode(_attrListRows);
+            // Round-trip through Decode to surface any un-parseable element
+            // (e.g. non-numeric in an Int32 list) before hitting the server.
+            try { AttributeValueCodec.Decode(attrValue, DataType.List, elementType); }
+            catch (FormatException ex) { _attrFormError = ex.Message; return; }
+        }
+        else
+        {
+            elementType = null;
+            attrValue = _attrValue?.Trim();
+        }
+
         var user = await GetCurrentUserAsync();
 
         if (_editAttrId is int id)
@@ -1573,7 +1657,8 @@
             var proposed = new TemplateAttribute(existing.Name)
             {
                 DataType = _attrDataType,
-                Value = _attrValue?.Trim(),
+                ElementDataType = elementType,
+                Value = attrValue,
                 IsLocked = _attrIsLocked,
                 DataSourceReference = _attrDataSourceRef?.Trim(),
                 Description = existing.Description,
@@ -1598,7 +1683,8 @@
         var attr = new TemplateAttribute(_attrName.Trim())
         {
             DataType = _attrDataType,
-            Value = _attrValue?.Trim(),
+            ElementDataType = elementType,
+            Value = attrValue,
             IsLocked = _attrIsLocked,
             DataSourceReference = _attrDataSourceRef?.Trim()
         };
diff --git a/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Shared/AttributeListEditor.razor b/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Shared/AttributeListEditor.razor
new file mode 100644
index 00000000..34e0dd26
--- /dev/null
+++ b/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Shared/AttributeListEditor.razor
@@ -0,0 +1,130 @@
+@using ZB.MOM.WW.ScadaBridge.Commons.Types
+@using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums
+
+@*
+    Repeatable list-value editor for a structured multi-value (List) attribute.
+    Reveals an element-type <select> (the six valid scalar types) plus one text
+    input per element with add/remove controls. Binds a List<string> working
+    model; the host encodes it to canonical JSON via AttributeValueCodec.Encode.
+
+    MV-14 reuses this component for instance overrides. Public API:
+      - ElementDataType  (two-way, bound)        : the chosen element scalar.
+      - Rows             (two-way, bound)         : the per-element string values.
+      - ShowElementType  (default true)          : hide the type <select> when the
+                                                    element type is fixed (e.g. an
+                                                    instance override inherits it).
+      - Disabled         (default false)          : render read-only.
+    Both ElementDataTypeChanged and RowsChanged fire on every edit.
+*@
+
+<div class="attribute-list-editor">
+    @if (ShowElementType)
+    {
+        <div class="mb-2">
+            <label class="form-label">Element Type</label>
+            <select class="form-select" value="@ElementDataType" @onchange="OnElementTypeChanged" disabled="@Disabled">
+                @foreach (var dt in ElementTypes)
+                {
+                    <option value="@dt">@dt</option>
+                }
+            </select>
+        </div>
+    }
+
+    <label class="form-label">List Values</label>
+    @if (Rows.Count == 0)
+    {
+        <p class="text-muted small mb-2">No elements. Use “Add element” to add one.</p>
+    }
+    else
+    {
+        <div class="d-flex flex-column gap-2 mb-2">
+            @for (var i = 0; i < Rows.Count; i++)
+            {
+                var index = i;
+                <div class="input-group input-group-sm">
+                    <span class="input-group-text" style="min-width: 2.5rem;">@index</span>
+                    <input type="text" class="form-control font-monospace"
+                           value="@Rows[index]"
+                           placeholder="@Placeholder()"
+                           @oninput="e => OnRowInput(index, (string?)e.Value)"
+                           disabled="@Disabled" />
+                    @if (!Disabled)
+                    {
+                        <button type="button" class="btn btn-outline-danger"
+                                aria-label="@($"Remove element {index}")"
+                                @onclick="() => RemoveRow(index)">Remove</button>
+                    }
+                </div>
+            }
+        </div>
+    }
+
+    @if (!Disabled)
+    {
+        <button type="button" class="btn btn-outline-secondary btn-sm" @onclick="AddRow">Add element</button>
+    }
+</div>
+
+@code {
+    /// <summary>The chosen element scalar type. Two-way bound.</summary>
+    [Parameter] public DataType ElementDataType { get; set; } = DataType.String;
+    [Parameter] public EventCallback<DataType> ElementDataTypeChanged { get; set; }
+
+    /// <summary>The per-element string values. Two-way bound.</summary>
+    [Parameter] public List<string> Rows { get; set; } = new();
+    [Parameter] public EventCallback<List<string>> RowsChanged { get; set; }
+
+    /// <summary>
+    /// When false, the element-type <select> is hidden — used where the element
+    /// type is fixed by the base attribute (e.g. instance overrides in MV-14).
+    /// </summary>
+    [Parameter] public bool ShowElementType { get; set; } = true;
+
+    /// <summary>Render every control read-only.</summary>
+    [Parameter] public bool Disabled { get; set; }
+
+    private static readonly DataType[] ElementTypes =
+        Enum.GetValues<DataType>()
+            .Where(AttributeValueCodec.IsValidElementType)
+            .ToArray();
+
+    private async Task OnElementTypeChanged(ChangeEventArgs e)
+    {
+        if (Enum.TryParse<DataType>((string?)e.Value, out var dt) && dt != ElementDataType)
+        {
+            ElementDataType = dt;
+            await ElementDataTypeChanged.InvokeAsync(dt);
+        }
+    }
+
+    private async Task OnRowInput(int index, string? value)
+    {
+        if (index < 0 || index >= Rows.Count) return;
+        Rows[index] = value ?? string.Empty;
+        await RowsChanged.InvokeAsync(Rows);
+    }
+
+    private async Task AddRow()
+    {
+        Rows.Add(string.Empty);
+        await RowsChanged.InvokeAsync(Rows);
+    }
+
+    private async Task RemoveRow(int index)
+    {
+        if (index < 0 || index >= Rows.Count) return;
+        Rows.RemoveAt(index);
+        await RowsChanged.InvokeAsync(Rows);
+    }
+
+    private string Placeholder() => ElementDataType switch
+    {
+        DataType.Int32 => "e.g. 42",
+        DataType.Float => "e.g. 3.14",
+        DataType.Double => "e.g. 3.14159",
+        DataType.Boolean => "true / false",
+        DataType.DateTime => "e.g. 2026-06-16T00:00:00Z",
+        _ => "text value"
+    };
+}
diff --git a/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Design/AttributeListEditorTests.cs b/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Design/AttributeListEditorTests.cs
new file mode 100644
index 00000000..654c7c5f
--- /dev/null
+++ b/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Design/AttributeListEditorTests.cs
@@ -0,0 +1,132 @@
+using Bunit;
+using ZB.MOM.WW.ScadaBridge.CentralUI.Components.Shared;
+using ZB.MOM.WW.ScadaBridge.Commons.Types;
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
+
+namespace ZB.MOM.WW.ScadaBridge.CentralUI.Tests.Design;
+
+/// <summary>
+/// MV-13: the shared <c>AttributeListEditor</c> reveals an element-type select
+/// plus a repeatable list-value editor for structured List attributes. These are
+/// real bUnit rendering/interaction tests over the self-contained component, plus
+/// structural assertions pinning the TemplateEdit attribute-form wiring (the page
+/// itself is heavyweight to render — see <c>TemplateNativeAlarmSourceEditorTests</c>).
+/// </summary>
+public class AttributeListEditorTests : BunitContext
+{
+    private static string TemplateEditMarkup
+    {
+        get
+        {
+            var dir = AppContext.BaseDirectory;
+            for (var i = 0; i < 6 && dir is not null; i++)
+                dir = Directory.GetParent(dir)?.FullName;
+            return File.ReadAllText(Path.Combine(dir!, "src", "ZB.MOM.WW.ScadaBridge.CentralUI",
+                "Components", "Pages", "Design", "TemplateEdit.razor"));
+        }
+    }
+
+    [Fact]
+    public void Editor_RendersElementTypeSelect_WithSixValidScalars()
+    {
+        var cut = Render<AttributeListEditor>(p => p
+            .Add(x => x.ElementDataType, DataType.String)
+            .Add(x => x.Rows, new List<string>()));
+
+        var select = cut.Find("select.form-select");
+        var options = select.QuerySelectorAll("option");
+        Assert.Equal(6, options.Length);
+        var texts = options.Select(o => o.TextContent).ToArray();
+        Assert.Contains("String", texts);
+        Assert.Contains("Int32", texts);
+        Assert.Contains("Float", texts);
+        Assert.Contains("Double", texts);
+        Assert.Contains("Boolean", texts);
+        Assert.Contains("DateTime", texts);
+        // List itself must never appear as an element type.
+        Assert.DoesNotContain("List", texts);
+    }
+
+    [Fact]
+    public void ShowElementType_False_HidesTheSelect()
+    {
+        var cut = Render<AttributeListEditor>(p => p
+            .Add(x => x.ShowElementType, false)
+            .Add(x => x.Rows, new List<string>()));
+
+        Assert.Throws<ElementNotFoundException>(() => cut.Find("select.form-select"));
+    }
+
+    [Fact]
+    public void Editor_RendersOneInputPerRow()
+    {
+        var cut = Render<AttributeListEditor>(p => p
+            .Add(x => x.ElementDataType, DataType.Int32)
+            .Add(x => x.Rows, new List<string> { "1", "2", "3" }));
+
+        var inputs = cut.FindAll("input.form-control");
+        Assert.Equal(3, inputs.Count);
+        Assert.Equal("1", inputs[0].GetAttribute("value"));
+        Assert.Equal("3", inputs[2].GetAttribute("value"));
+    }
+
+    [Fact]
+    public void AddElement_AppendsRow_AndRaisesRowsChanged()
+    {
+        var rows = new List<string> { "a" };
+        List<string>? changed = null;
+        var cut = Render<AttributeListEditor>(p => p
+            .Add(x => x.Rows, rows)
+            .Add(x => x.RowsChanged, r => changed = r));
+
+        cut.Find("button.btn-outline-secondary").Click();
+
+        Assert.NotNull(changed);
+        Assert.Equal(2, changed!.Count);
+        Assert.Equal("", changed[1]);
+    }
+
+    [Fact]
+    public void RemoveElement_DropsRow_AndRaisesRowsChanged()
+    {
+        var rows = new List<string> { "a", "b" };
+        List<string>? changed = null;
+        var cut = Render<AttributeListEditor>(p => p
+            .Add(x => x.Rows, rows)
+            .Add(x => x.RowsChanged, r => changed = r));
+
+        // First per-row Remove button.
+        cut.FindAll("button.btn-outline-danger")[0].Click();
+
+        Assert.NotNull(changed);
+        Assert.Single(changed!);
+        Assert.Equal("b", changed![0]);
+    }
+
+    [Fact]
+    public void EncodedRows_RoundTripThroughCodec()
+    {
+        // Mirrors what TemplateEdit.SaveAttribute does on submit.
+        var rows = new List<string> { "10", "20" };
+        var json = AttributeValueCodec.Encode(rows);
+        var decoded = AttributeValueCodec.Decode(json, DataType.List, DataType.Int32);
+        var list = Assert.IsType<List<int>>(decoded);
+        Assert.Equal(new[] { 10, 20 }, list);
+    }
+
+    [Fact]
+    public void TemplateEdit_RevealsListEditor_AndSendsElementType()
+    {
+        var markup = TemplateEditMarkup;
+        // Conditional reveal on DataType.List.
+        Assert.Contains("_attrDataType == DataType.List", markup);
+        Assert.Contains("<AttributeListEditor", markup);
+        Assert.Contains("@bind-ElementDataType=\"_attrElementDataType\"", markup);
+        Assert.Contains("@bind-Rows=\"_attrListRows\"", markup);
+        // Submit encodes rows to canonical JSON and passes the element type.
+        Assert.Contains("AttributeValueCodec.Encode(_attrListRows)", markup);
+        Assert.Contains("ElementDataType = elementType", markup);
+        // Edit decodes the stored JSON value into rows.
+        Assert.Contains("DecodeListRows(", markup);
+    }
+}