ModifyQueueWatchers

A user with the Modify'Queue'Watchers right can modify (add or delete) queue watchers.

This right does not allow the user to modify watchers of the individual tickets.

This right can be granted to users in the global context, or on a queue-by-queue basis

If you want to grant users the right to add or delete themselves as watchers then you can use the rights Watch, WatchAsAdminCc and ModifyTicket (but this last right does not allow a user to add or delete himself as a queue watcher?!?)

See also: Rights, GlobalRights