Microsoft has officially released reassigning and unassigning users from Personal AVDs. The feature is cool and allow administrators to reassign/unassign AVDs faster. Let us see how we can do it via Azure portal. I haven’t seen any direct command line which will perform the un-assignment of user.
Unassign a user from personal AVD
Navigate to Azure Portal –>Azure virtual desktop–>Host pools –> Click on session hosts.
Select the session host which need to be reassigned or unassigned from the user. From the top menu, click on Assignment and select “unassign user”.

A confirmation window will appear asking you to confirm with the un-assignment. Select “unassign” to remove the user mapping from the AVD.

Assign the AVD to another User
To reassign the AVD to another user, click on the “Assign to a different user” option under Assignments.
A new window will appear where you can select the new user name and once selected click on “Assign” to reassign the AVD to the new user.
