I've recently upgraded my GS350 with heated steering wheel and I've been in look for this option of buttons for couple of months now. Anybody ever seen one like that or know exact part number?

This photo is taken from some Russian marketplace. The closest I've found by description is this https://parts.longolexus.com/oem-par...nel-8401030860 with part number 84010-30860. Which goes with description: Haven't found any photos of 84010-30860. Tried to reach out to https://parts.longolexus.com and some other dealers which has this part for some photo confirmation, but non of them approved that this is the part.

 

According to Amayama, and going by description, it can be any of these three. The difference being what other options do you have on your car.
https://www.amayama.com/en/genuine-c.../electric/8401

This one is likely what you posted. Just traction and steering heater but no auto high beam button
https://www.amayama.com/en/part/toyota/8401030860
STEERING WHEEL-LEATHER, WITH(STEERING HEATER


This one has a 3rd button for headlight functionality in addition to heater button. Likely for turning the Automatic High Beam on and off. So it is traction, steering heater, and auto high beam.
https://www.amayama.com/en/part/toyota/8401030k30
STEERING WHEEL-LEATHER, WITH(STEERING HEATER)&HEADLAMP-LED(PROJECTOR) & WITH(*AHB)

On mine, I don't have heated steering, but do have auto high beam, so mine is likely Toyota 84010-30L10. I also have traction control button, but that is likely on all the options, so it doesn't have to be mentioned in the product description.
HEADLAMP-LED(PROJECTOR) & WITH(*AHB)

Note the year it is applicable. Since you didn't post it, I search for 2016 +.

 

You may have to go with a different button layout (like the image below) or possibly even having to replace the dash trim to accommodate a button layout that works for you.

 

@EAST Mine is 2015. Yes, as far as I understood, traction button goes for all layout options, so it is not mentioned on any of it.
That's all the options I have on mine Default traction, and now heated steering wheel. So this button layout would be perfect for me.

@bclexus Yes, you are right. If I don't find the one I'm looking for, I will have to go with different button layout. But I really would like to avoid having buttons (or empty buttons) for features I don't have on my car

 

With yours being a 2015 you have to look at build month then.

As there are different part numbers for the pre facelift.

https://www.amayama.com/en/genuine-c.../electric/8401

Toyota 84010-30840
COLD AREA SPEC&STEERING WHEEL-LEATHER(DIMPLED), WITH(STEERING HEATER)

Toyota 84010-30860
STEERING WHEEL-LEATHER, WITH(STEERING HEATER) but only for March through September 2015 builds.

This looks like it has a button for blind spot on/off
Toyota 84010-30850
STEERING WHEEL-LEATHER, WITH(STEERING HEATER)&BLIND SPOT MONITOR-WITH & WITH(REAR CROSS TRAFFIC ALERT)

There's a couple more but you get the idea.

 

I'm betting with your diligence and imagination you'll be able to come up with an interesting use for any blank or empty button.

I recall one member ingeniously added a momentary mute switch/button for his radar detector in the blank tab.