[PatK]

Is it possible to create folder type nodes based on path? Or is it possible to have multiple sources within one node?

In the library node editor, add rule, title should bring up a requester that includes 'path' (browse for value) you can have multiple rules/paths in one node, plus multiple nodes (most of the rules are the same as smart playlists).

my music library split up in 2

Should do, create two nodes or use smart playlists and call them into the nodes. six of one half dozen of the other... nodes may offer different features. I haven';t gone down this rabbit hole far enough to tell you if there will be issues with Yaste and a headless Kodi (I don't think this is supported directly) Perhaps you can enlighten us?

genre and it took more than 10 minutes

Naw: nothing takes 10 minutes in Kodi outside of a full scrape. Either a scrambled library or stumbling on the scraper. Duplicates are almost always duel different paths to the same thing, clean-up should take care of this if the library is not compromised. I knew you didn't want to hear that. Check  the path for duplicates and see if they point to the same file but a different path, usual issue if 'sources' scanned while nested-sources in the same folder are also 'sources'.

Side note Kodi 19+ atm has issues with the library node editor.