Even if the person is a manager and you get the error :
Changes to the distribution list membership cannot be saved. You do not have sufficient permission to perform this operation on this object
Then make the following changes in Powershell.
To grant permission for an individual run :
Add-ADPermission -Identity:'Group Display Name’ -User:domain\username -AccessRights ReadProperty, WriteProperty -Properties 'Member'
To grant permission for a security group :
Add-ADPermission -Identity:'Group Display Name’ -User:'Display Name of Permissions Group’ -AccessRights ReadProperty, WriteProperty -Properties 'Member'