well i ones added a capture mouse to my 3d game. also made in godot. and its not realy that hard. if you know how to capture a mouse. there is also a way to undo it. i suggest working with the ESC button and the click button. so like when you click ESC the game freeses and your mouse is visible. but wen you click it becoumes invisible or you can us a UI element like that. forinstance "continue" but i would suggest having an ESC logo at the top of your game. or i would add the info to your start screen of the game
I never said it's hard, I was imagining, e.g. my mother clicking "run this game" and then panicking when she wants to leave the site .. not the experience I want to give people who did not come onto this link knowing of itch.io in advance.
but an explicit "ESC" in the top left might be an instructive hint, maybe "retake mouse" or something like that :D