Am I missing something here? (Searched)
Clearly you can long press traction to disable it but is there a way to go all off on the RC350 like you can with RCF?

 

Is this what you are looking for?

Turning off both TRAC and VSC systems
 RC350
To turn the TRAC and VSC systems off, press and hold for more than 3 seconds
while the vehicle is stopped.
The VSC OFF indicator light will come on and the “TRAC OFF” will be shown on the
multi-information display.*1
Press again to turn the systems back on.
 RC F
To turn the TRAC and VSC systems off, press and hold ( ) for more
than 3 seconds.
The “TRAC OFF” indicator light and the VSC OFF indicator light will come on.*2
Press ( ) again to turn the systems back on.
*1: On vehicles with PCS (Pre-Collision System), pre-collision brake assist, pre-collision
braking, and steering control (performed through cooperative control of PCS and
LDH) (if equipped) will also be disabled. The pre-collision system warning light will
come on and a message will be displayed on the multi-information display. (P. 290)
*2: On vehicles with PCS (Pre-Collision System), pre-collision brake assist and pre-collision
braking will also be disabled. The pre-collision system warning light will come on
and a message will be displayed on the multi-information display. (P. 290)

 

I believe the best we can do is TCS off (3 sec) and Sport+ Mode. It's standard procedure when I get in my car every morning.

 

Thats what I wound up doing but found that the pedal dance which works on FRS and other Lexus/Toyotas will disable all of the assists.