Probably a dumb question, but my owners manual doesn't seem to cover this. On the ceiling, a few inches from the controls for the sunshade and parking assist is a yellow light that never seems to go off. Any idea what this is?

The parking assist button lights up a different red indicator on the button itself.

 

It helps illuminate the centre console area at night. Makes it easier to swap CDs etc.

 

. . . and provides an uber smooth ambiance . . .

 

Its called a "mood light"

Seriously