Hm, after a couple of hours of play, here are some small changes I could see:
On the sister groups screen where you can allocate the formation points (cute, cool, sexy, etc.) it'd be helpful if there was a way to undo an addition: I didnt know what was happening at first and accidentally sorted one of my points, and there's no way to undo it. A "cancel" option so you can leave that screen without saving if you make a mistake would be nice.
More designation between groups would be a godsend:
1) In the production/released tabs: I was working on two groups' singles simultaneously and they look identical, perhaps you could chose a color when you make the group too, and all their associated "tabs" retain that color for distinction's sake?
2) On the girls' job sections, maybe it could take a page from Stage48 and list singles like this:
Akizaka46
Give Me Six
Sounds Great
Tartan Plaid
Sakazaka46
White Goat
instead of just having all the titles one after one another chronologically? (As in, Give Me Six releases on July 2018, Sounds Good on Aug 2018, but the idol participated in the sister groups' White Goat on Sept 2018, and then the full group's Tartan Plaid again on October 2018. Instead of WG following Sounds Good, it's separated to indicate which group the song came from.)
3) Following that, the tooltip for formations on the released single tab already looked a little cramped with how it tried to represent positions with written names, but now that there are sister groups I think it would be helpful if it showed maybe a list, rather than a comma-separated paragraph, split by group, and then displayed the formation when you clicked on the single's "card". The different groups' singles being tabbed separately instead of all being listed chronologically would also help!
Finally this is kind of a bug, but during the single formation screen, it will wipe your formation if you switch the group tab. The main group tab also retains all your hires across all groups, not sure if that's on purpose.
Thanks for reading! Still got lots to play, lol