Once a playlist grows past a few hundred tracks, doing it by hand stops working. These articles cover where people actually get stuck and how to get past it — useful to read even without the tool.
Why the same track ends up in several playlists, and how to tell apart duplicates inside one list from tracks that overlap across lists.
How to pull near-duplicate playlists together, and what to watch out for when you do.
How to let a group add songs to one queue that plays in order, using nothing but a Bluetooth speaker.
Genre or situation, and how many lists is too many. Setting up rules that survive the next six months.