Nothing to worry! Spotify is undertaking some changes and Songs folder name is now Favorite Songs. Another change is that the + and Follow buttons are changed to a ♥︎.
You will be able to Follow artists and playlists by tapping that heart which will add the to Your library, but don't worry they won't be added to your Favorite Songs yet. When you open a playlist or when exploring an artisits page for songs you can tap ♥︎ again this time to save them in Favorite Songs.
Spotify has done this change to make one universal icon to add something to your library! ♥︎
Have a nice day!
Help others find this answer and click "Accept as Solution".
If you appreciate my answer, maybe give me a Like.