It's shown as a single (up and down) dealer enabled custom option in my handbook. I can't see the benefit of enabling just one direction?
One can (on my 2019 RC) also use the mechanical key to do the same thing, once the setting has been made
Lexus tend not to fit looms for options not included in the build.
One would also need a change to the centre console to accommodate the button plus there must be a module somewhere to control the timer function..
I looked at lowering my RC300h but the only springs available were for the petrol variants without AVS. I was advised not to go ahead as spring rates would be wrong and would cause issues with the AVS.