I think he is talking about nested playlist (.m3u) files, not nested playlist nodes in the tree.

Something similar to that was already requested in Mantis: Ability to play nested playlist files needed

lots of dj's in here so you should have got an answer by now? but you can use autoplaylists to point to another playlist. i just don't do it so i can't remember how.
some of the other dj's here should know if peke is not busy programming he might be able to help

Any chance it could support nested playlists? What I need is for it to be able to read a .m3u8 referencing another .m3u/.m3u8.
It's fine if the playlist gets flattened on import though some visual hint that several songs came from a nested playlist or even ability to move them together would be nice.

The thing is ... I am a tango DJ and the building block of a tango playlist is not a song, but rather a tanda: 3 or 4 songs from the same orchestra, same mood, same era .. selected to fit together. Most people like to prepare the tandas beforehand and then just select and order the tandas, add some cortinas (non-tango songs cut to 30-45s used as a separator). I've got plenty of old .m3u8 playlists that are nested ... the main playlist contains references to the tanda playlists.