I've found out article: https://www.comparis.ch/autoversicherung/news/2014/02/navi-geraet-falsch-montiert-busse.aspx
It states that mounting GPS navigation on windscreen can make you subject to hefty fines, if it blocks your view in anyway.
My car (Fiat Panda) has vents shaped so, it's impossible to mount GPS on them. I've found out no other potential place other than windscreen. Is it possible to mount it there in such a way, I won't be subject to fine? If so, how to do that? Are there any official graphics, for example, showing how to mount it to comply to Swiss law?