After installing YouTube Music Desktop App and enabling plugin Shortcuts it’s possible to use D-bus commands.
I had to identify the bus so ended up with https://unix.stackexchange.com/a/46309/39470
dbus-send --print-reply --dest=org.freedesktop.DBus /org/freedesktop/DBus org.freedesktop.DBus.ListNames
string "org.mozilla.thunderbird.ZGVmYXVsdA__"
string "org.mpris.MediaPlayer2.brave.instance1661"
string "org.mpris.MediaPlayer2.youtube-music"
string "org.pulseaudio.Server"
Now I could test if it works
dbus-send --print-reply --dest=org.mpris.MediaPlayer2.youtube-music /org/mpris/MediaPlayer2 org.mpris.MediaPlayer2.Player.PlayPause
dbus-send --print-reply --dest=org.mpris.MediaPlayer2.youtube-music /org/mpris/MediaPlayer2 org.mpris.MediaPlayer2.Player.Next
dbus-send --print-reply --dest=org.mpris.MediaPlayer2.youtube-music /org/mpris/MediaPlayer2 org.mpris.MediaPlayer2.Player.Previous