I still have the old EN business account before v10 came out. I sort of do this chat notebook already with 2 other colleagues on the business account. the attachment is a template that shows how we "chat" in the note and how we use notelinks for a client's case. We take turns in editing the note. Sometimes my colleague forgets to "release" the note because he's gone off to do something else, and the note's locked for a long time, so I would have to ping him or DM him that I need to edit the note.
I also have a new personal account that i just bought (as it was 50% off) and I'm curious to see if multiple users of upto 3 can share this one account and using the same way of "chatting". I could use it for family and household management or for a different team in a different region. But I did sign up to Slack as you suggested. ... and already I am loving it. But the chat note will probably remain, as it's sort of like a logbook/table of contents of a notebook showing events that transpired. But it's not really chatting... but I like the idea of categorising chats so youre right slack is probably a much better alternative and i'll just integrate EN.
At any rate I will be subscribing to Teams as well for the experience.