I don't think that you can disable the sunshade from going down when the car is in reverse, but I'd ask when I next have the car in for service. I've never seen that item on a menu of changes, customizations or adjustments.
My recollection is that free customization adjustments are offered for 3 months after purchase, or maybe at the first service. I'm sure it's less than 3 years, but many dealers will make a change for you if the car is there for something else.
You have been living with this annoyance (safety feature) for three years, so that says something.
But ask at the dealership - there may be a hidden code somewhere.

 

Programmable by Dealer
12. Automatic Rear Sunshade* The rear sunshade automatically lowers when the shift lever is shifted into Reverse.
o Off
o On (Default)
See: https://www.lexus.com/content/dam/le...ES_LPS_CST.pdf

 

In the Lexus Personalized Settings form I referenced above in post #12, see "Programmable by Dealer" item 12:
From the reference form:

 

If you know someone with an OBD dongle, you can do it with Carista (trial for free) [edit] Can't find the trial anymore.

 

Thanks for the updates on this feature which, it turns out, can be turned on/off.
In my experience, sometimes your can get a customization changed at a service, but that's at the dealer's option. Be sure to ask if there is a charge for this before they take the car to the service area.
Or, as noted, some of the OBD readers like Carista will let you do this yourself.
For the most part, since I got my ES over a year ago, I have only put up the sunshade when the granddaughters wanted to see it go up, just for fun. Even then, they don't pull up the manual ones on the side windows.

 

Thanks for the info!
im super out that window frame.
I love the sunshade cause I don’t have tints on my car personal preference.
car has never been serviced at dealership
My friends does my oil change and tire rotation!!
cars been a tank since new!!
just got a broken ac vent after the car wash but I didn’t noticed until a few days later . Plus like a dummy I use a heavy *** vent mount on the piece on it was a matter of time anyways
( I’ll just glue it back if it’s a whole center console removed to install the that piece)
I never go to car washes but it’s been the whole winter with no wash so I went f it just to get most of the dirt off and just wash the car myself at the DYI gas station washer pressure.!
I have my personal extension brush and my Xxl microfiber cloth to dry it
I just don’t want to burn out that motor since I’ll probably drive it till the wheels come off since the next gen is not for me or just drive my s class so I’ll just find someone outside the dealer since I have have no time to sit and wait for those jerks.!!
I will

Drive side ac vents broken on my side and the clips is like a size of a pencil lead cheap car markers!!
post a pic of the vet. Hopefully there’s a way to fix it without going through so much trouble. Many thanks again.

 

Most likely you must remove the whole thing to fix it. The pin broke or snapped out?

 

That little thing is broken .!!
The side toars the hazards are double while toars the cluster is single.!!
even if it’s under warranty I don’t feel comfortable from they removing the whole center console and radio .!
I guess I’ll just use I think it’s called e6000 or something and call it a day.!!! A type of clear glue or something
I got a new phone holder that clips between the hazard lights with adjustable direction!!
I’ll probably install it one day..!!
I’ll take this than owning a used German car out of warranty any day !!! It was so bad the cable for the hood latch broke so you can imagine how many times the hood was popped up!!