Say there’s a playlist that gets regularly updated on an external service such as SoundCloud or Spotify. The Spotify “Discover Weekly” playlist is a good example.
Suppose you want a playlist in Apple Music that gets updated with any new tracks that appear in your Spotify “Discover Weekly”.
That’s what the Sync function is useful for: each time you import “Discover Weekly” with Sync mode switched-on, instead of simply creating a new playlist (e.g. “Discover Weekly (2)”) Playlisty will compare the Spotify version of “Discover Weekly” with the version in your Apple Music library and it will add any new tracks to the end.
Maybe “Add mode” would be a better name for it than “Sync mode”?
Also, if you don’t want to have to remember to do the sync every week you can setup a Siri Shortcut to do this for you, using the “Add to Siri” button on the final “Save” screen, and then creating an “Automation” in the Apple shortcuts app. For more details on how to use Playlisty within Siri Shortcuts, click here.