This is the first time I noticed this but there's a button behind the glovebox top left, icon of a car and open trunk. Has ON/OFF, does anyone know what it's for. I'm guessing related to trunk function?

I usually either use my key fob or the one under the driver's dash. So I have no idea what this other one is for. Anyone know?

 

This disables the trunk function in the event you give want lock out the trunk when using a valet service. The valet key will start the car, but it will not unlock the glovebox so the on/off switch is protected. I've used it a few times; comes in handy if you have to leave something valuable in the trunk while you're out.