You can now lock Group Rosters / Availabilities as a Staff member to prevent students from booking further sessions, even if slots are available. For example, if you want to reserve the last time slot for a specific student until they're able to confirm, or if you want to prevent other students from booking this time to provide more attention to a single student.
This option is available within your Group Roster window as a lock icon at the top, click to toggle on or off.