Hi,
I did a lab test in my environment.
After copying your XML file, my start menu was also locked. But if I copied below example, and replace "<DefaultLayoutOverride>" with "<DefaultLayoutOverride LayoutCustomizationRestrictionType="OnlySpecifiedGroups">", the start menu will not be locked.
<?xml version="1.0" encoding="utf-8"?>
<LayoutModificationTemplate
xmlns="http://schemas.microsoft.com/Start/2014/LayoutModification"
xmlns:defaultlayout="http://schemas.microsoft.com/Start/2014/FullDefaultLayout"
xmlns:start="http://schemas.microsoft.com/Start/2014/StartLayout"
xmlns:taskbar="http://schemas.microsoft.com/Start/2014/TaskbarLayout"
Version="1">
<LayoutOptions StartTileGroupCellWidth="6" StartTileGroupsColumnCount="1" />
<DefaultLayoutOverride LayoutCustomizationRestrictionType="OnlySpecifiedGroups">
<StartLayoutCollection>
<defaultlayout:StartLayout GroupCellWidth="6" xmlns:defaultlayout="http://schemas.microsoft.com/Start/2014/FullDefaultLayout">
<start:Group Name="Life at a glance" xmlns:start="http://schemas.microsoft.com/Start/2014/StartLayout">
<start:Tile Size="2x2" Column="0" Row="0" AppUserModelID="Microsoft.MicrosoftEdge_8wekyb3d8bbwe!MicrosoftEdge" />
<start:Tile Size="2x2" Column="4" Row="0" AppUserModelID="Microsoft.Windows.Cortana_cw5n1h2txyewy!CortanaUI" />
<start:Tile Size="2x2" Column="2" Row="0" AppUserModelID="Microsoft.BingWeather_8wekyb3d8bbwe!App" />
</start:Group>
</defaultlayout:StartLayout>
</StartLayoutCollection>
</DefaultLayoutOverride>
<CustomTaskbarLayoutCollection>
<defaultlayout:TaskbarLayout>
<taskbar:TaskbarPinList>
<taskbar:UWA AppUserModelID="Microsoft.MicrosoftEdge_8wekyb3d8bbwe!MicrosoftEdge" />
<taskbar:DesktopApp DesktopApplicationLinkPath="%APPDATA%\Microsoft\Windows\Start Menu\Programs\System Tools\File Explorer.lnk" />
</taskbar:TaskbarPinList>
</defaultlayout:TaskbarLayout>
</CustomTaskbarLayoutCollection>
</LayoutModificationTemplate>
I compared your xml file with this example, and found that you missed some lines. Your file didn't contain the lines in below red frame about start layout. I am not sure if you removed them before you post them. But I can confirm the start menu will not be locked after adding these lines.
Please have a test in your environment.
Also, you can just export the start layout using powershell command "Export-StartLayout". And then add the taskbar layout configuration just after "</DefaultLayoutOveride> "
</DefaultLayoutOverride>
<CustomTaskbarLayoutCollection>
<defaultlayout:TaskbarLayout>
<taskbar:TaskbarPinList>
<taskbar:UWA AppUserModelID="Microsoft.MicrosoftEdge_8wekyb3d8bbwe!MicrosoftEdge" />
<taskbar:DesktopApp DesktopApplicationLinkPath="%APPDATA%\Microsoft\Windows\Start Menu\Programs\System Tools\File Explorer.lnk" />
</taskbar:TaskbarPinList>
</defaultlayout:TaskbarLayout>
</CustomTaskbarLayoutCollection>
</LayoutModificationTemplate>
For your reference:
https://www.makeuseof.com/tag/use-group-policy-for-custom-windows-start-menu/
Thanks,
Eleven
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