you want two buttons.....

one master to turn the LC on,

and one mounted on the clutch pedal, so when the pedal is right up the lc is off...

then you dont need any buttons as such to operate the lc, when the clutch pedal is down sat at the lights the lc is operating, when you pull off and the pedal comes right up it will switch off, when you are driving normally swotch the master off

used to have this system on an old car of mine ,had full throttle gear change too