I recently added the ability to select some cards and move them to a new space (screencast: https://twitter.com/KinopioClub/status/1296205302988025856)

The idea is that if you've got a bunch of cards you want to 'group' to isolate and expand on seperately, it's pretty convenient to be able to do so in a new space.

Let me know if this addresses grouping for you, thanks :)