The ability to click on a song that you have added to your playlist and see from where you downloaded it. For example, if you search a for a song that you have already added to your playlist previously, you would be able to see where you added it to your playlist from. Ex. Click on the song and a little message in the corner allows you to see from where you downloaded it. This way you can sort songs in a playlist by searching from where you found that song. Ex. Search among a private playlist: "This is Michael Jackson" and all songs that you have added from that playlist will appear. "This is Michael Jackson" is an arbitrary playlist created by Spotify.