I can’t replicate that issue on a similar setup (slightly newer OS). I opened schematic editor, clicked Add Symbol, interacted with that modal window for a bit, then CMD+Tab’d away and back. Returning to KiCad still shows the Symbol Chooser window as expected. I did notice that the display-all-windows button (F3 on the Macbook Pro US keyboard) does not show the modal window, but it correctly comes to the front for me when selecting any of the KiCad main windows.
Ok, I guess I realised what’s going on. I had enabled the “AltTab” window manager for switching between all windows of all applications via CMD+Tab. Once I disabled it, it’s not possible to switch between windows, but it works for Kicad. Now I’m able to go back and the modal window is on the top. Is there a quick way (maybe a shortcut) between switching the windows and not apps?
And no, I’m using just a one display. On the other hand, once I press F3 for showing all windows and I switch to other app than Kicad and back to schematic with opened modal window it doesn’t work. I’m in the same situation like before. But … the “workaround” works. Once I press CMD+Tab and back, it works.
But at the end, I would say it’s a bug anyway. Because if you read my last comment at the issue it works during debugging session.
On Mac, you can generally switch between windows of the active application with Cmd+Backtick (top left of a US keyboard). That has been inconsistent in KiCad, in my experience.
There are two open issues related to the Cmd+Backtick just… stopping working randomly. I could imagine this might be related to what you’re experiencing? If so, consider giving this issue a thumbs up: