So if I understand well, you can’t manage to get the screeching alarm sound while continuing the music at low volume.
If I were you, I’d merge all parameters in one labelled parameter, called, say, “Progression”, with 4 values : Ambient (0), Lasers active (1), Protection active (2), Game Over (3). Set the volume automation of Mission Impossible track for values 1 and 2. Open the parameter sheet and put the screeching alarm sound in it, at value 2. Don’t put the sound in the timeline. The Progression parameter going from 1 to 2 (or from 2 to 1) should be set to have no impact on the timeline (so the music to play continuously).
However if you want to keep things as they are, you should put your SFX in the “Lasers active” parameter sheet, at value 0, with the trigger behavior condition “Button pressed” = 1.