To add icons to the Stack, users simply drag and drop them right ... from the handset's primary home screen, or any other page of apps given that it integrates with the stationary dock.

Once you create a stack, navigate to the home page and you'll see the stack icon—but instead of having a plus sign in the middle, it will have a rightward facing arrow to indicate "play." ...

Although Windows 11 shows icons in an Overflow menu on the Taskbar, it is possible to stack or unstack icons on the Taskbar using this tutorial. You can do that with the help of the Registry Editor.