Being able to check or look over things that have happened (such as an idol liking you, or an idol losing mental stamina). I know there is a notification but it's easy to forget so being able to look back would be nice. And maybe some indications of why certain girls are losing mental stamina, as it's easy to forget.
Being able to bring up your fan demographic breakdown while planning your single would be nice, so I know what genres would be good.
I would also like to be able to name events.