So I've asked around and got the following information:
After first launch of the game you don't need to login in-game anymore, you're identified via your steamaccount.
If you've switched steam account, it will prompt you to create a new account. If that's the case, send an email to feedback@musegames.com and they can swap the accounts.
I still don't understand what your problem is, so I just hope this helps ^^'
