OOTB as you mentioned it only allows you to add “Alias” or “Calculated” attributes from Type and Attribute Manager and this is expected behavior because if you look at WTUser class from JAVADocs i.e wt.org.WTUser class you will see that it does not implement the IBAHolder interface . If IBAHolder Interface is not implemented by that class then you cannot associate IBA’s or soft attributes with that class. This behavior cannot be customized since the class cannot be extended and is expected to only allow addition of either alias or calculated attributes. If you look at other Windchill Objects like WTPart or WTDocument you will see that they implement IBAHolder interface which in turn allows a user to create soft attributes or IBA’s for them.
