Via the access dialog of an appointment, its creator or organizer can grant fixed authorizations (e.g., write permission) to another staff member (backoffice) so that the appointment can be processed and closed "on order".
Editing appointments on behalf of someone
See also: Protection of records, Concept of fixed access
Activated fixed access (the column with small lock in the access dialog) also ensures that changing the access authorization of a connected case does not affect the access authorization of the staff member concerned ("on order").
Note: If the appointment is a delegated one, it must be accepted at least by the new responsible to be able to process it with fixed authorizations.