I did some search, but still I don't find a solution.

The buttons on the dash (flasher, ESP, heated seats); just go inside the dash if pressed firmly.
I had to remove the stereo and cut myself, trying to reposition them. Problem is....they fall in again.

From what I read, there is a plastic sliding plate, parallel to the stereo cage, that slide out, so you can access the buttons; and there should be a sort of mechanism that plug behind each button to keep them in position.

I do not see that plastic tab, that should go behind each button. They are just stliding in the dash hole and clip trough the side clips that the buttons have; there is nothing behind them.

Am I missing something, or the retainer that was supposed to be there, was removed/broken by the previous user?

I can be gentle, but it may happen that I push with too much strength and loose the buttons again; so I am looking for a definitive solution.
I am surprised at how Audi engineered that part of the dash...Germans have big hands