Playlist folders/playlists at the collection level are still there in 5.8.1. and they work perfect even when switching between 5.6.0 (which I need to use to import XML data) and 5.8.1.
However if you talk about iTunes (music.app) playlists/folders, things become a bit more problematic. The iTunes tab doesn't always show the playlists which are enclosed in a playlist folder on the iTunes bridge level. However if you import that playlist-folder to the collection all of a sudden the enclosed playlist show.
See this example: the base iTunes collection:
How Rekordbox (any version past 5.6 really) shows it in the iTunes tab, notice the "test2" playlist which is part of the "boem" folder is missing under the iTunes tab.
After importing the "boem" folder the playlist "test2" shows up in the collection part of Rekordbox (its still missing from the iTunes tab)
I forgot the most important part.. how to fix it ;)
- goto the Sync Manager (left lower hand corner of the Rekrodbox preparation screen)
- disable iTunes sync
- quit Rekordbox
- start Rekordbox
- enable iTunes sync (and ensure the playlists you want to be sync'd are checked)
and all is fine again ;)