You can reassign a task that is already assigned to one processor, and reassign it to another processor by unassigning the task from the user. Unassigning the task moves the task back to the queue where you can assign the task to another work queue processor.
Users with the queue_admin or queue_manager role can unassign a work queue task from a user.
To unassign a work queue task from a user:
Click Work Queue Monitor.
Navigate to the active work queue, and click its name.
Select one or more tasks that have already been assigned to users.
Select Tools > Work Queue Management > Unassign.