Will playlist songs be added to my library after I turn the setting on?

I didn't realize that when I added a playlist to my library, each individual song was not being added to my library. I turned the settings on to have songs be added to my library when I add a playlist, but the songs from previous playlists that I already saved did not get added to my library. Is there a way to add all those songs from previously saved playlists because I have so many and I didn't know they were not being added to my library.