I was trying the new component for QoS Class Map that is in the 20.2.5 release in an interface context, but it doesn't show any data.
Not supported at this time.
Release : 20.2.5
Component : IM Reporting / Admin / Configuration
It's not a DB column. It's a special RIB field that on the DA side will take the parent device of the current item and then try and find all items that support the metric family being queried and use those item_ids in the query instead. Yes, code would need to be added to use .Hierarchy.ParentID when the metric family is not for the current item context (like QoS metric family for an interface which only really supports Interface metric family). This currently not supported at this time.