Remote Toggling between Line In and Amp In

I want my clean sound to be amplified by PS2, and the dirty sound to go through the reactance load attenuated.

I remember talking to support in 2018 and there is a trick where a stereo jack carries the signal into the Amp In (I think-my memory is fuzzy) on one channel, and a remote close/open contact switch on the other channel- giving me a toggler switch between Reamplication (Line In input) and Attenuater (Amp In input).

Anyone gone deep into this territory?