https://manual.yoyogames.com/GameMaker_Language/GML_Reference/Cameras_And_Display/The_Game_Window/window_set_size.htm is what your looking for. be careful of blurry aspect ratios.
#Is there a quick workaround to trying to resize the window of my game?
granite smelt
coarse terrace
If I add this to this one room--cause there's obviously multiple rooms in the project--will it apply to all of the others?