Batch Operation
This tutorial explains how to perform batch operations against multiple issues
Assumed Scenario
For all open Windows issues assigned to tommy or jerry, reassign to robin
How to Set Up
Change to issues page of desire project, and filter with below query:
"State" is "Open" and "Platform" is "Windows" and ("Assignee" is "tommy" or "Assignee" is "jerry")
Click the Batch Edit All to change assignee to robin and save