Hello Maheshwar!
The eazy (sic) way is to add “Assignee” both on Rows and pages then select multiple users as needed. This works if you don’t have to do it very often.
If you need a permanent solution check this: How do I group users under a single row? (Logged by)
Or this: How to filter unwanted statuses
You’ll have to create a group in ASIGNEE dimension, using aggregate.. except, then use it in your report.
Hope it helps!
Vasile S.