Unless I have missed something, I have not found a means to illuminate the lighting control stalk on the left side of the steering wheel. The other two stalks on the right side of the steering wheel are also unlighted, but only the cruise control stalk and the lighting control stalk should be illuminated for night time use. My vehicle is a 2014 ES 300h.

 

My 2013 UL is not lit.

 

You are correct it is not illuminated. A PITA at night...

 

Are you looking for illumination to see where the stalk is to reach it?
If you just want to know what position each element of the stalk is in the dash displays
one or more lit icons to confirm the left side lighting control stalk settings.
The green "lantern" shows that the main low beams and various body marker lights are on.
The green "down cast light" shows that the fog lights are on. A blue light shows high beams.
Optional in 2014 and standard since 2017 will show an "Auto High Beam" in green as long as
a separate (unlit) lower dash button is pressed.

 

Since I leave my lights set to "auto" I have little reason to be looking at the stalk either during the daytime or at night. However you make a good point as it's all displayed on the IP. Didn't think of that...