UPDATE: SmartPlaylist v9.1 has now been released.
Update delayed, because Apple now wants me to remove all album artwork in the screenshots shown in the App Store ... (for more than six years this was no problem)
The next version of SmartPlaylist (v9.1) will also offer to search by Album Artist, in addition to or instead of Artist.
You can make the following settings (in Menu > Settings ...):
- Show / hide rules: Show or hide Album Artist
- MusicBrowser: Show / hide: Use either Artist or Album Artist for the hierarchical Music Browser (e.g. Genre > Composer > Album Artist > Title)