Merging scattered playlists into one
"Driving", "Driving 2", "Driving new" — lists split like this all the time. You cannot search your existing lists every time you make a new one, so it is a natural outcome.
Decide the axis first
Pick what the split means. The two common axes are genre (K-pop, J-Pop, Pop) and situation (workout, sleep, driving). Mixing them is what makes lists split again.
If you organise by genre, resist making a "workout" list; if you organise by situation, do not keep parallel genre lists. If you truly need both, let one of them be playlists and treat the other like tags.
What goes wrong when merging
First, duplicates. Similar lists share tracks by definition, so a naive merge adds the same song three or four times. Merge by video ID so each track lands once.
Second, order. Merged order is usually meaningless. If you had carefully arranged a list, ask whether that order still matters before you dissolve it.
Third, it is not reversible. After merging you cannot tell which list a track came from. Keep the source lists around for a while instead of deleting them immediately.
Why you cannot move everything at once
Each track added to a playlist counts as its own write against a daily quota. Several hundred at once will stop partway.
In practice, merging 100–200 tracks at a time is the realistic ceiling. Beyond that, split it across days or move only the tracks you actually want.
Playlist Manager collects the tracks from the lists you pick, removes repeats by video ID, and creates a new private playlist. Your original lists stay untouched. Playlist Manager →