App opens windows to extended display

[fiat]

I am running M2 Pro Mac mini with Ventura 13.3.34. When I run an app (e.g., Gimp) in the Main display, it sometimes needs to open a sub-window and then another sub-window. The first sub-window usually resides over the main app window in the Main display (that's normal), but the second sub-window would open in the extended window! This is bothersome especially since I usually turn off my extended display to conserve display life and only turn it on when working specific App on the display. When I ran the same app on my old Mac mini with El-Capitan 10.11, no same issue occurred. I wonder if there is a way to set that each app's main window and all sub-windows can open in the Main display, not the extended display? Appreciate any help.