How to combine Smart Playlists with Favorites

Audirvana 3.5.46

I have made a smart playlist of HighRes music files (by bit-depth greater than 16). Works fine. But how to combine this with my List of Favorites, so I’ll end up with a playlist of my favorite HighRes files?
There seem to be no references to Favorite in the choices for building smart playlist - or for the matter - reference to other existing Smart playlist, so you can combine them…

Any Suggestions welcome… /Steen