Missing headlight level adjustment knob

Hello,
while I was replacing the lights of the ABS button, seats heaters etc...I've found that there's a cover on a button near the left seat heater button. Under this cover there's a grey plug with cables. Which is its function? If I fit a headlight level adjusting knob (that shoul have a grey connector), can I adjust the headlight level. All the cables and motors on the headlight are present?
Any other suggestion?
Thanks in advance.
Nicola