Once upon a time it was possible to copy many songs at once, or an entire playlist, and paste it in another playlist (or drag). Now I can't do that anymore.
The thing is, I have created a playlist for every year and I have done that since 2013. Now I figured I would like to have one playlist that has all of the songs from different years. But I can't copy the whole playlist and drop it in the new playlist. I'm not really motivated to do that one song at a time.
In this case, we suggest to move the songs from the desktop app. If you have a Windows computer, you can select all the songs you want to move within a playlists with "Ctrl + A" ("Command + A" for Mac). Then, you'll only need to drag the songs to the playlists you want them to be in.