The playlist/Media library has a few issues that are not yet resolved. I use VLC mainly on Windows but I think these issues are general. What I've found is the following:
* One cannot add whole directories in the media library, especially directories on shared networks (Windows/CIFS), the player reports "file not found"
* When adding files (or creating directories) in the media library, one cannot add them directly into the subdirectories, everything is created in the root, even though the subdirectory is selected
* Oh, and the regular playback controls (e.g. spacebar for play/pause, bluetooth headset buttons, ...) don't work when the playlist / media library window/pane (CTRL+L) is opened/active.
* One cannot edit the properties of the items in the media library. If I for example created a directory with the wrong name, the context menu item "Information" gives the possibility of editing details of items in the library. The problem is that whatever is edited in the "information" window will not be saved when closing it. One cannot rename items using F2 either.