Does anyone know how to change the cover for custom playlists?

I began making a few playlists of my own in Nintendo Music & I’ve noticed something strange regarding the cover images.

As you see in my Pokemon Battles playlist, the cover is that of a SV song, cause that’s the first song in the playlist.

However for my other playlists, it shows the first 4 songs.

Is there a way to change that, so it only shows the first one, like for my Pokemon Playlist?

I even tried adding only one song first & then add others, but then it goes to 4 again.

Does anyone know how to do it?

I only found out how to change the name of a playlist and order of songs, but it’d be so nice if there’s a way to change the cover as well.