I thought that was an easy one. No matter how I do the logic or priorities it ties the three button functions in a knot. The funny thing is when you hit the center both button, the outer left and right buttons depress on the skin. Every scenario I could think of, the best I got was this. Center button works as it should, hold it down it turns on both outputs until you let go. My front LH and RH buttons will only pulse their respective outputs. Files attached.
Non-software solution is a third FB output driving a third relay that energizes the first two (RH and LH).