Users can select a "private" subset to use in a View for one of the view's dimensions.
Since the subset is private, it's only usable for that specific user. If they would now save this View as "global" (meaning, all other users can see & open the view), it couldn't work correctly. Thus, it would be useful if the UI would simply prevent saving such a View as a global one (in all places where views can be saved as global), best with an indication for the user why it isn't allowed.
The feature would also need to account for a user specifying a Private Subset after a view has already been created & saved, and then saving the updated view.
