the author rights should be not deleting a appointment, but only canceling the appointment, can I change the rights somewhere?
Maybe you have another solution.
you want to disable deleting appointments for admin user? Or you want to disable it for all?
acl for actions is not passible at the moment. Solution would be to block call for deleting Appointments by custom code change. If you want that I can guide you what to change.
Mybe it is possible to change the butten “delete” in to “cancelled”.