Okay, it can't have been SHIFT+WIN+{arrow} that I used for that, since I use SHIFT+WIN+{left/right} to flip a window between screens (on the same desktop). I'm now using SHIFT+CTRL+WIN+{arrow} and this works. I assume that something in the OS is locking whatever combo I was using before, but my muscle memory isn't giving me that combo. This ticket can just be closed now.
Some combos including WIN not working after update to Win11