Um, this is exactly what the article is about: Tesla used to do this. There used to be a persistent "defog" button right at the bottom, but now it's hidden behind the Temperature indicator, which looks like it only lets you adjust up/down.
The article is about being unfamiliar with a car after 5 minutes. If the button was a physical button you’d still have to look for it since you are still unfamiliar with the car.
Before downvoting, ask yourself:
* “Would this article exist if the person found the button within 5 minutes?”
* “Would this article exist if the person was familiar with the car?”
> This is one reason why hard-buttons are so effective in old-school cars. They all use these same standard icons so it’s easier for new users to scan across them and find the one you want without any training.
Imagine a physical button for the demister that's hidden behind a temperature display LCD that hinges down.
There's no indication that the temperature display moves or reveals anything, no affordances, other than on a statement on page 3-11-A of the vehicle manual. Would it be acceptable to be confused in that instance even after many five-minute periods?