Yes, we should always ask ourselves what we don't know, there is always something to learn! If you don't know, ask here - that's why we mentor each other! And, when you get the answer (which has happened in this case), it is memorable!
I support the suggestion that the nav lights are found on the instrument dimming roller switch. That is where I have found them in the past, when I was looking around PA-28's I was flying. My experience has been that that switch function was labeled, but the words might wear off with time, and finger tips wearing on the nearby plastic. So perhaps, the placarding which was there has faded...
Also, that switch function has a bit of a fussy "engage the toggle switch yoke" type mechanism, which has been known to fail. Thus it might be possible to have working instrument lights on the roller, but the nav lights do not function. That could be puzzling, and would be a call to maintenance...
There are a few isolated things on various types, which really ended up being tribal knowledge, as they were missed during certification. The nav light operation in a PA-28 tends toward this in my recollection. Another example of things that a pilot will never figure out, and cannot determine by reading anywhere in the aircraft, would be how you transfer the wing tank fuel in a Lake Amphibian into the main. Best get type training for that, 'cause it's way too simple to ever figure out while you're flying! (I used the "phone a friend" option!
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