Sorry it was mxa who tested it....
HOW DOES KTM’S LAUNCH CONTROL SWITCH WORK?
A: Last year a rider had to cycle the flip switch on the right side of the bars back and forth until the indicator light behind the front number plate flashed. For 2017 the rider has to press the rubber-covered map button and the traction control button simultaneously until the indicator light behind the front number plate flashes. This is easy to do with gloved hands or if the gate is getting ready to drop. You have to plan ahead because it takes two hands. Of supreme importance is that once launch control is engaged, you must refrain from blipping the throttle. If you rev the engine up and let the revs fall by more than 30 percent, launch control will shut off—and you cannot reengage it without shutting the engine off.
MXA test riders rarely use launch control on dirt starts, but we use it all the time on concrete. Everybody has his own method for using launch control off the line, but the majority of MXA test riders hold the throttle wide open and dump the clutch. The retarded ignition curve knocks off several horsepower to decrease the chance of wheelspin. You should practice starts to find out how much throttle works best for you.