Depois de passar algum tempo procurando a resposta, finalmente consegui fazê-la funcionar.
Basta editar seu arquivo spotify.desktop
em /usr/share/applications
[Desktop Entry]
Name=Spotify
GenericName=Music Player
Comment=Spotify streaming music client
Icon=spotify-client
Exec=spotify %U
TryExec=spotify
Terminal=false
Type=Application
Categories=Audio;Music;Player;AudioVideo;
MimeType=x-scheme-handler/spotify;
Actions=PlayPause;Next;Previous;Stop
[Desktop Action PlayPause]
Name=Play-Pause
Exec=dbus-send --print-reply --dest=org.mpris.MediaPlayer2.spotify /org/mpris/MediaPlayer2 org.mpris.MediaPlayer2.Player.PlayPause
[Desktop Action Next]
Name=Next
Exec=dbus-send --print-reply --dest=org.mpris.MediaPlayer2.spotify /org/mpris/MediaPlayer2 org.mpris.MediaPlayer2.Player.Next
[Desktop Action Previous]
Name=Previous
Exec=dbus-send --print-reply --dest=org.mpris.MediaPlayer2.spotify /org/mpris/MediaPlayer2 org.mpris.MediaPlayer2.Player.Previous
[Desktop Action Stop]
Name=Stop
Exec=dbus-send --print-reply --dest=org.mpris.MediaPlayer2.spotify /org/mpris/MediaPlayer2 org.mpris.MediaPlayer2.Player.Stop