Template/Assets/TaskbarLayoutModification.xml

<?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">
  <CustomTaskbarLayoutCollection PinListPlacement="Replace">
    <defaultlayout:TaskbarLayout>
      <taskbar:TaskbarPinList>
        <taskbar:DesktopApp DesktopApplicationLinkPath="%ALLUSERSPROFILE%\Microsoft\Windows\Start Menu\Programs\Contoso App.lnk" PinGeneration="1"/>
        <taskbar:UWA AppUserModelID="Microsoft.WindowsCalculator_8wekyb3d8bbwe!App" PinGeneration="1"/>
        <taskbar:UWA AppUserModelID="Microsoft.WindowsTerminal_8wekyb3d8bbwe!App" PinGeneration="1"/>
      </taskbar:TaskbarPinList>
    </defaultlayout:TaskbarLayout>
 </CustomTaskbarLayoutCollection>
</LayoutModificationTemplate>