It would be really nice to do changes over multiple sessions for things that take a while without having unfinished content on the page.
You totally can. See the radio buttons at the very bottom of your game's editing page. I think draft mode is even the default.
but does this work when a game is already published, and you want to change things without updating the published version but you don't want to unpublish it either
Ah, that's different. Not to my knowledge.
I think this could be helpful but not sure how I could integrate it into the current edit flow easily, since there's a lot of stuff that happens when you click save. I'll think about how we might be able to add this in the future.