In Music, how can I get newly uploaded albums into an existing playlist that I can sync to my iPad?

On my wife's iMac with Sequoia 15.7.2, I recently uploaded some albums from my purchased CDs using a connected external drive. When I drag an album to add it to a playlist, I get a popup "Cloud Music Library playlists can only contain songs from your Cloud Music Library/If you continue, [playlist name] will be removed from your Cloud Music Library and will only be available on this computer." I don't remember seeing this with previous OS versions.