I want to suggest the implementation for resizable stage manager, so we can use the full resolution of the external display.
THEY LISTENED TO US!!
On the last TestFlight’s version (5370) the support of stage manager is finally stable!!
It supports resizing and also changing resolution from the menu (It dynamically change while stretching of the app).
Nice work Microsoft, thanks. And also thank all of you that have commented and upvoted this suggestion!