When editing a service you'll now find a field to set the max concurrent reservations per Appointment board.

This is for scenarios you can only manage going back and forth between a limited number of clients at a time.

You can turn this option on under Appointments > Services > Select service > Edit > toggle on Limit max. concurrent reservations.

Note: this service requires enabling overlapping of appointments by venue and staff. You can do this by editing a board and toggling these two settings on.

Below, Rachel is teaching a group climbing class where she's booked up 3 customers for the same service.

And because her max number of concurrent reservations is set at 3, she'll see this message when attempting to book a 4th customer for the same service at the same time.