I’m probably missing something obvious but I want to able to play chords with Engine 1 but have a mono sound on Engine 2, is there a way to do it?
The short answer is no as the voice number is global.
However, a not so elegant method is to set the global voice count to monophonic but use the Chord function in one of the engines. You will be limited to the available chords and need to map them across a region of the keyboard as well as setting up a keyboard split for Engines 1 and 2. Not ideal at all.
Maybe this could be considered a feature request?
Edit: you could achieve this in Analog Lab as it support 2 instruments in layer or split mode. Just add the mono and poly patches and set up the split.