Does anyone know if you can add expansions in the middle of a campaign? Or is the campaign generated based on your collection when you start it? Waiting for trollfens and another to arrive but want to begin it today, wont bother if they are not going to be integrated though :/

It's malleable. (Yes, it will change.)

Cheers!

This would just be for the monster groups that get chosen though, and items available from the shop decks, right? Aren't the campaigns predetermined which bosses you fight in each quest?

I've removed things from my collection and been told by the app that I could no longer play a saved game that was started when I had the item.