Archive
You can archive your tracks so they no longer appear anywhere in Lexicon, but they are not completely gone yet. Archived tracks only appear in your Archive (under Tracks) and in the playlist they were already in when the track was archived.
Your archived tracks will keep their cue points and all their data. They are simply placed in the convenient archive so you can sort them out or delete them at a later time.
You can archive tracks by right clicking them in the track list. You can un-archive tracks by right clicking tracks in the music archive.
Playlists
When you archive a track directly from within a playlist, the track is removed from that playlist immediately. If the track also appeared in other playlists, it will still be there. When you archive a track from the track browser (without being inside a playlist), the track will still appear in all your playlists.
This is so you can archive tracks without worrying about breaking your playlists.
When you run the cleanup, the tracks are also removed from all your playlists.
Cleanup
Lexicon can help you clean up your archived tracks. Use the Selection helper to automatically select tracks that have already been in the archived for some time. You can also tell Lexicon to only select tracks without cue points or tracks that don't appear in any playlist.
When you have selected tracks you want to get rid of, press the Cleanup selection button. By default, your tracks will only be removed from Lexicon. If you want, you can also remove them from your computer.
Keep in mind that removing from your computer is permanent, so make a backup if you are unsure.