You can find the window with the class spotify.Spotify, and then identify it by window ID.
wmctrl -lx | awk '-F ' '$3 == "spotify.Spotify" {print $1}'
You can find the window with the class spotify.Spotify, and then identify it by window ID.
wmctrl -lx | awk '-F ' '$3 == "spotify.Spotify" {print $1}'