I am new to Plex music, however not new to managing large music libraries. Is there a way that a user can create "Multi-level Smart Playlists? 
Coming in from Apple Music (formerly Itunes), a user could create a smart playlist comprised of other smart playlists. Essentially a primary smart playlist draws tracks from sub smart playlists which are defined by specific criteria and update dynamically.
When interacting with larger libraries this is an excellent way of managing the weighting of genres in a smart playlist, acting as a sort of primary key, to keep the music fresh and balanced. Essentially a tool to create your own radio station.
None of the cloud music services can even offer this sort of granularity.
I’m more of a visual person, see the example flow below.
Example of one of my primary 35 tracks smart playlists which draws from other smart playlists from iTunes. At Christmas time I like to sprinkle in a 4 or 5 tracks holiday smart playlist.
Individual Smart Playlist Close Up. 
(As per request)
#Recently Added • 7 (tracks)
#Higher Love • 3 (tracks)
Of note — “Higher Love” is homage to an excellent Depeche Mode track of the same name, check it out. 
Mod-Edit: moved this post in the existing feature suggestion which is already covering this (in order to avoid distracting votes/attention) – though I suppose the screenshots / mockups help to better visualize what you’re looking for!
