Stage Manager is confusing as hell. It was designed for iPads in an attempt to give them some semblance of window management but even there it makes no sense. They tried to reinvent window management to be more "simple" but in doing so they made something WAY more complicated to the point where even computer-savvy folks can't figure out how to do basic tasks.

https://youtu.be/sFJuAjyWOc4?t=500