It is a direct answer to the original question posed by David in the post that started the thread:
"Does anyone know the trick to opening the GROHE shower mixer for servicing?"
That is literally "the trick" to opening the shower mixer then there is no screw at the top. You use a screwdriver to pry it off. Given that this forum is comprised of people from all around the world, many of whom are not native English speakers, I find that posting pictures in addition to text can be very helpful, even for something as "simple" as a water faucet service.
SM #440 Cara
Deale, MD USA