Well, I was going to suggest that the easiest thing to do, albeit a bit drastic, would be to cut the track going to the topmost pin marked red in your picture (same as the signalwire going to the knobboard is connected to) and ground it, but I checked on a displayboard and the other 3 leds are connected together with a track which goes to a via coming up under a chip. I don't know if this is the PIC controlling the buttons (didn't want to bend open the vfd to look), would possibly have to cut this track too... So it's probably best to let Schofiel tell us what the best thing would be, which probably would be "Leave it alone"...

Stig