How do I move an appointment to another time, day or staff member?

Tap the appointment in the Schedule, press "Edit" and change what you need: date, time, service or staff member. If the service is split into stages, changing its time re-assigns the staff for the new time. When you press "Save changes" it does not ask you about the client notice: you already have the change in front of you, in the form itself. If you move it to a time when the staff member already has another appointment, it tells you before saving and you save it with "Save anyway"; if it was deleted while you were editing it, the form tells you and stays open.

In Plan you can also drag it to another slot. There is no form to look over there, so if the client is going to be told about the change, it asks first: "Move this appointment?", showing from where to where and "Juan will get a notice with the new time", and you choose "Move" or "Don't move". That happens when the appointment is pending or confirmed, changes day or time and the client gets the "Appointment moved" notice. If nothing will reach them (you only change the staff member, the appointment is already closed or there is no way to reach them), it moves straight away, and the dashboard notice offers "Undo" in case you got it wrong.

When you change the day, time or location of a pending or confirmed appointment, the client gets the "Appointment moved" notice with the new time, through the channels you have switched on in Settings › Communication › Automatic notices, and their reminders go out again for the new time. The dashboard notice confirms it: "We've let Juan know."

And if what you want is to bring someone forward because an appointment dropped, do it from Gaps: there the dashboard tells you who to offer it to.