How do I access the "Hidden Menu" on 07 D3 S8 MMI?

I know it’s done through VCDS but how?

It might be already activated : hold “car + setup” for like 6 seconds, if nothing happens, then it’s via VCDS.

VCDS > module 07 “head unit.” > adaptation - 10 > channel 08 :
_ stored value : 0
_ new value : 1

Then “car + setup” and you should be good. Just so you know, there is no way to know the oil temp for sure via the MMI.

Thank you!

No problem. Just let us know if it worked !

Now that I have the “Green” screen what are kool things that I can do with it?

Well, my first advice would be to be careful. Easy to create a mess fiddling around the menu. I just activated it so i could check the battery level in the mmi after.
Sadly, no way to get the oil temp on the S8 d3 plateform.