Waitlist
A waitlist records clients who want an appointment slot that is already full, so they can be offered it if someone cancels.
Also called: cancellation list, standby list
A late cancellation is only lost revenue if nobody knows the slot has opened. A waitlist sends a message about the opened slot to people who already asked for that time.
Waitlists work best on the slots that are genuinely contested. A list on a quiet Tuesday morning collects nobody and teaches clients the feature does not work.
Booked's waitlist applies to sessions that are full on capacity, which is why it covers group sittings rather than every one-to-one appointment.