I’m not 100% sure, but I believe that I cannot add the flag metadata field to a photo. Spotlight works through “metadata importers” – one per file type. The system provides the importer for images, so I cannot replace it and add my own stuff. It is probably possible to add metadata a different way, but it would not be the flag. I have read articles that it’s possible to add metadata to a file using Finder comments and then find them using Spotlight (as a user) – something similar is probably possible for the code.
As far as Ratings go, that is also not in the app. I would have to look at it more to see – if Spotlight reads XMP ratings, then I could conceivably add ratings via XMP but that would require RAW Power modify the original file, which is something I don’t do (for safety reasons).
Smart Folders are Finder objects – they are not real File System objects (like files and folders). As a result, they cannot be added to RAW Power (only the Finder knows they exist).
Sorry for all the “no’s”.