The best way to keep track of an arbitrary group of songs is to put them into a playlist.

You don't need the playlist to be something that gets played. You can mark the playlist "Ignore as child", for example.

I've got a few playlists that are there as just a holding pen for special stuff. All of my lyric-tagged songs are in their own playlist, for example. This also helps for when I want to demo Emphatic.