But please, how does one "add tracks from playlists" using this tagging mode?
You can use tagging mode to add tracks
to playlists by selecting tracks in the list and then clicking in the empty tagging check box.
You can remove tracks from a playlist by selecting tracks in the list and then clicking in the populated check box.
This can be really handy for managing playlists that will be synced to a handheld device, for example, which may require one final tip:
Add a smartlist to your playlist group that includes all of your audio files, but excludes all of the other playlists in the group. Now, when you select this entry in the pane, none of the files in this list exist in any of the other playlists, and can be added by selecting files and ticking the tagging mode check boxes. Hitting refresh updates the list removing those files that have just been added to playlists. New playlists can easily be added to the group right there in the pane using the "New Playlist" entry shown at the bottom of the pane when files are selected.
Playlist sub-groups, though they cannot be created directly in the pane, also work, showing up in the pane as expandable/collapsible playlist branches! So simple, yet so powerful.
-marko.