I typically use activities to separate work, school, and personal leisure. So if I got some school work partially done I can Meta+Tab back to my personal stuff then return back to the School activity with everything as is to pick right off from.
Now it seems like that’s been removed and activities are still a thing, but windows follow whatever activity I’m on at the time. Normally if I need a window elsewhere I can right-click the titlebar, Activities, and pick the one, but that’s not there either.
KDE Plasma Version: 5.26.5
KDE Frameworks Version: 5.102.0
Qt Version: 5.15.8