How do i change in bulk manager name for specipic distribution list
PowerShell will help you out here. Get-ADGroupMember will get you the contents of your list, and Set-ADUser will modify the parameters of each user.
You're looking for something like
That will show you what users it's making the change to, and confirm that it can find the new manager name you gave it. When you're satisfied, remove the -WhatIf to actually make the changes.