Unable to add albums to new playlist on Mac OS Music app

I just subscribed to Apple Music.

I want to create some playlists of my favorite albums using the Music app on my MacBook Air.

I searched for an album, found it and then created a new playlist from that album.

I searched for another album, found it, then tried to add it to the playlist that I just created, but the playlist does not appear to allow me to add to an existing playlist.

HELP