Yes indeed, it is either the location for dimmer switch, or sunroof or mirrors? Not sure about it since I only know the locations of 5th gen Civics a bit (and they are on the same spot approximatly). But dimmer switch gets the best change from me.
So, just get a dimmer switch and plug it in? Cool... would be a nice mod to do .
look, if you see the first picture you can see that the button on the sunroof and mirrors is at the bottom of these buttons!
someone has opened that lid to see if it also has that connector?
If this is not the dimmer switch, then it is for sure the rear fog light switch.
Check out if your rear fog light is working if not it is due to the unconnected switch.