Bookly has a useful undocumented feature that helps a staffer to fill up their daily schedule with no gaps. Assume all services are 1 hour long, in a system with time steps of half an hour. If an employee starts at 9:00, then Bookly will only offer appointments starting on the hour (9:00, 10:00, etc). If an appointment was permitted to start at 10:30, there would be no way for the staffer to fill up 100% of their day.
But for collaborative services, it seems that this feature is not implemented, if it contains more than one simple service.
Certainly, this feature is slightly more complicated to implement for multiple staffers, but it could be done easily, and would be useful.
I have a collaborative service that uses 4 simple services. Each simple service is associated with one staffer who starts at 9:00. My system uses time steps of half an hour, for other services. But for this one, I wish it would restrict the start time to start on the hour.