There are two kinds of note, and the rule for which to use is one sentence: if it's about this visit, write it on the visit; if it's about the person, write it on their profile.
A visit note
Open the booking and type into Visit note: what you did and what to do next time. It saves when you click away. It's also in the close-out, with last time's note above it. A visit note shows on that appointment's card on the calendar (see Calendar settings), on the booking, and under that visit in the customer's history. Short by nature, because it sits on the card.
Notes on the profile
Open the customer and go to Notes. Write anything about the person that isn't about one visit: the session write-up you keep on file, the history behind a colour, what they told you about their wedding. Notes here take bold, italics, lists and links, and can be as long as they need to be. Each one carries the date and who wrote it, and says edited if it was changed after. Newest first.
Each visit's note shows in the same list, read-only, marked with the visit's date and service; tap it to open the booking. Notes are written on the booking, and read here alongside everything else on file.
A note on the profile never shows on the calendar or on a booking, with one exception: a pinned one.
Pinning a note
Some things must be in front of you at every visit: an allergy, a preference, a warning. Open the note's menu and choose Pin. A pinned note sits at the top of the Notes tab and shows under Previous notes on every booking of theirs, above the earlier visits. Unpin it and it drops off them all.
If you kept a note on the customer before this tab existed, it's here as your first pinned note.
Who sees them
Your team only, and never the customer: not on the booking page, not in any email or PDF. Anyone who can open the client book can read them; anyone who can take bookings can write, edit, pin and delete them. Deleting a note is for good.
Where did the Notes box on the side go?
Into the Notes tab, as the first pinned note. It still shows on every booking of theirs, exactly as before.
Can a customer's note come across with my customer list?
Yes. A notes column in the file you import lands as a pinned note on each customer, so it shows on their bookings from day one. See Import your customers.