To enable the waitlist in online booking go to:
Settings > Online Booking > Preferences
When a client selects a day and does not find a time that works for them, they can use the Join Waitlist button.
Once completed, they will be automatically added to the waitlist and notified that their entry has been added.
Once an opening becomes available an internal notification can be sent to staff, and the waitlist opening notification icon will appear on your calendar.