You can no longer edit a song from the playlist

Sorry - why is this?? Thought that functionality was quite useful.

Yes -sorry, that was a useful feature.
However, there are some issues when the playlist song has been changed to have a different display type, key, and capo key. A song can be edited to be quite different from the one in the playlist. It can change to minor and even remove the titles and replace with new ones. And now with the new sharps/flats feature there is even more going on.
Therefore the edit from the playlist has been removed temporarily until it can be replaced with a limited type of edit.
This will allow you to edit just the lyrics and chords, so it will still be a useful feature. All full editing will continue to be done from the main list.
Hope that makes sense?