Is there any API to add the contents of an album or a existing playlist to a new playlist? Based on the current documentation, it seems that only addition of a track to a playlist is supported. I'm hoping to avoid bulk add (by fetching the content of a playlist) and then adding them as tracks.
There are nice convenient APIs to add an album to MyLibrary. It would be nice to have something similar to add an album to a playlist.
There isn't currently a way to do what you ask. You have to get all the track ids from the playlist or album and then add them to the new playlist. You can bulk add the tracks, at least, but you'll still have to do it in two separate steps for now.