The title pretty much explains the problem. Previously, with XFCE, using the keyboard shortcut I had set in the settings manager had changed keyboard layouts on a per-vm basis, but now that Im on KDE it seems like I have no way to change keyboard layout outside of the Qube Manager.
Either a fix on how to do this through KDE or the commands that Id need to do to write my own scripts to change keyboard layouts would be wonderful 
Thanks ahead of time for the help!
The problem persists for KDE now (4.3). Does anyone know a solution to make Alt + Shift a permanent function in an appVM? After rebooting appVM it stops working again, even though the settings haven’t changed. @alimirjamali or someone KDE users, please help 
I also noticed that if I run sudo thunar in terminal, Alt + Shift working again 
Hi. To clarify, KDE Wayland or KDE X11?
default KDE desktop x11 from KDE (desktop environment) — Qubes OS Documentation
It seems that when I enable second keyboard layout in dom0 before start appVM, switching Alt-Shift works in appVMs (but I’m not sure - it didn’t work in one of appVMs). I still don’t understand the pattern of how this works 
Is there a workaround for this issue? Keyboard layout switching only works in dom0 but it is not working in any other VM in Qubes 4.3?
I would like to emphasize this issue because KDE is rather neat out of the box in Q4.3.1 and this problem is probably one of the few burning issues there are. It exists in Qubes 4.3.1 with KDE, in both X11 and Wayland sessions.
For X11, the corresponding Github issue should be this one: https://github.com/QubesOS/qubes-issues/issues/10571