just an "undo" button in general is welcomed

Honestly, it's a pretty bad option. Many if not all games implemented these days on BGA have undo, and an option to not use a timer. There are always things you might miss and once you added the card it's too late to do anything about it. Given that you don't reveal any new information unless you choose to replace some cards or tokens, it would feel much better to have step by step undo. I know that it's a cost in terms of development, but it turns the game from something I'd actively avoid (with no undo) to something that I'd play quite often.

It's a bit tiring to fight on many games for an undo option, only for it to be added later when more people complain...