click on Project → Project Settings → navigate to WINDOW → check “resizable”, mode “viewport”, aspect “keep”. that should keep your windows with always the same content and adjust the viewport according to any resolution, adding black bars to excess or odd resolutions.
you can try it out toggling full screen with a switch
OS.window_fullscreen = not OS.window_fullscreen
I don’t think that’s what they’re asking… they’re asking about multiple resolutions, I think.
exuin | 2021-02-16 17:10
made a more complete answer now, with those options checked the resolution should keep your viewport size (things shown) in any resolution you end up using