might not be a problem of KStars, but under Raspbian Bullseye 64bit my taskbar is about only half of the screen in width. When I limit the taskbar width to 720 px, it is complete:
When increasing width, it is cut off:
I'm running a screen resolution of 1920x1280 in VNC (with HDMI dummy, but without dummy and 1920x1080 it is the same). Maybe someone came across this problem and found a way to solve it? Didn't find anything on Google, not even a hint...
When I remove the "Desktop Pager" from the taskbar panel it expands over the full screen width as it should. For my multiple desktops I use the desktop switching hot keys (shift-alt-left and -right) instead...