Where does this custom inventory data "live" at runtime?

In the editor. My problem is grasping how to write code that the rest of the team can easily work with in the editor for the design level stuff. When I say drag and drop I mean I make a TArray<UBaseItem*> items but in the editor, if they make a BP from a BaseItem, then try to assign the BP to the array in the editor, they can’t. It appears to ONLY accept a UBaseItem, not a BP derived from UBaseItem.

That said, I just stumbled upon TSubclassOf<> so I am going to try that soon as I get a chance.