Say there’s a playlist that gets regularly updated on an external service such as SoundCloud or Spotify e.g. perhaps a friend shares their favourite tracks in an “On Deck” playlist which they add to each week.
Suppose you want a playlist in your Apple Music library that gets updated with any new tracks that appear in that their “On Deck” playlist.
That’s what the “Add to existing playlist” (aka “Add Mode”) function is useful for: each time you import “On Deck” with Add Mode switched-on, instead of simply creating a new playlist (e.g. “On Deck (2)”) Playlisty will compare the Spotify version of “On Deck” with the version in your Apple Music library and it will add any new tracks to the end.
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.