Hi Jason - thanks for your interest in EurekaSound.
So, I think you're asking for "effect state probing" - where the FCB1010 would use to MIDI commands to read the effect unit's state in order to reflect that state with the LED on or off. This only works on a very limited number of effects units (AdrenaLinn, Behringer V-Amps, Fractal Axe, & Kemper Profiling Amp), and is not something that is supported by Mainstage.