- Go to User > Roles > Add new reg role
- Define Permissions
- Go to Site Admin > Content & Data > Documents and Media or any app that libraries are applicable to
- Click the Change button to select some sites
- Click save
- On the permission summary page, click Remove button
Only can remove one site at a time, but the confirmation message says: Are you sure you want to remove this permission?
And unable to choose which site to remove.