Smart organization in saved messages: since it's hard to navigate through them atm, some kind of organization is totally needed. Not sure about the ai though

Slow mode notifications: had hard time imagining use case scenarios for that, but probably it has to do with the rapid-fire delivery of messages when they sent at a time? Then I'd suggest no special setting for that – let it be inbuilt

Collaborate editing: the more I think of it – the more convincing it looks. Must be devastating to loose your edits due to someone's overwrites, while editing together simultaneously.