Subpanels in user module showing assigned records

In the users module, the detail view of a user should include subpanels for assigned records. For example, I would like to see all quotes and invoices this user is assigned to.

I already tried to enable the default quotes subpanel for the aos_quotes_assigned_user relationship in /custom/working/modules/AOS_Quotes/relationships.php , but after a rebuild nothing changed.

Does anybody have an idea I could try?