Restrict app to monitor

Hello!

Is it possible to restrict an app to a specific monitor or X11/Xorg coordinate region?

I am running Steam in Flatpak on openSUSE Leap 15.4 (X11). The game Civilization 5 always starts in the primary monitor. I can force-move it to the other monitor with KDE/kwin, but it still determines the maximum available resolution by the primary monitor (my second monitor is larger).

If there was a way to restrict the available X11 canvas to just be the second monitor (Steam/Civ only see the second monitor with coordinates starting there), then I think that would solve the issue.

The other solution is to temporarily change my primary monitor, but then notifications are covered by the game, panels are swapped, etc.

Thanks!

Not possible via anything Flatpak related

Ah, I see, thank! Was worth asking.