A number of new options appear when you press the Edit button.
The red circle just to the left of the song’s artwork allows you delete a track from the playlist altogether.
The app will always ask you to confirm the deletion before removing the song so you don’t have to worry about deleting anything accidentally.
And, of course, the song is only deleted from this playlist, leaving the original song as part of your music library.
A red ‘+’ sign has also appeared in the top-right of the screen as well, so you can just tap this to add more songs to the playlist whenever you want.