Is there a way to perform system wide power scaling

The “power” in LightBurn corresponds to a pulse-width-modulated value ranging from 0% = no power to 100% = full power. How the machine translates that PWM signal into actual laser current is up to the controller, not LightBurn.

For CO₂ machines, physics also gets in the way, because the tubes do not fire at less than about 10% of their rated current; your 130 W tube may not fire at less than 15% or so. 

The high-voltage laser power supply has an analog potentiometer behind a tiny hole somewhere on its case to set the tube current when the controller calls for 100% power. You can adjust the pot so 100% produces whatever current you think appropriate for the high end, so that 100% = full throttle.

The trick is to set the power to 50%, then twiddle the pot until the supply delivers half the maximum current you want. The relation isn’t exactly linear, but it’ll be Close Enough™ for practical purposes.

So, basically, LightBurn will have a minimum power around 15% that will fire the tube and a maximum power of 100% (or 99%, whatever) adjusted to produce the tube’s rated maximum current.