i don’t know about Godot, but if you don’t assign mouse input to anything in your game in GameMaker, there simply is no mouse input. you don’t have to disable it with extra code. i would assume this is how all game engines work, but maybe Godot is different?
Yes in Godot you can use a collection of GUI controls like buttons and dropdown menus and stuff. By default they all respond to mouse events, which are handled a bit differently from button inputs in godot. It’s a doozie for new users so this is a way to ensure any mouse input that does reach the game is eaten regardless of however the game is set up.