I am sure, I have seen the GAFOR routes in an earlier version or on the trial.
Nevertheless, I actually don't see GAFOR routes with the "OMX" indications in Austria or Switzerland.
I have the latest version (3.6?)

At least in Switzerland I can see small, grey dotted lines where I usually find the GAFOR routes
Can I switch them on ?

On iOS and Android there is a switch to enable GAFOR in the Weather menu.

You'll see them light up if you plan a route in those countries.

Okay, that worked for me.In Planning mode, I can see the routes.
But while flying (yesterday using X-Plane as Location Service) it seems looking different

Are there any Information about the needed altitude available ?

What do you mean by needed altitude?

Same problem here:
In SD 3.6.0 (iOS) the GAFOR routes in Slovenia (including the "OMX" information) light up, but not in Austria and not in Swizerland. In those countries I only see the dotted grey lines. I downloaded already weather for all of the maps/countries and "show GAFOR" in the weather menue is switched on

@Tim:
"needed altitude": Every GAFOR route in Austria comes with a reference altitude, that indicates the lowest safe altitude to fly along this specific route

To see the route number, reference level and current route status, just press and hold your finger on the route in question to bring up the "What's Here? menu on your iOS device

I can answer my own question now:
Austrocontrol issues the first GAFOR diurnal at 5AM (Zulu Time), but it's valid only as of 6AM. Basically Slovenian GAFOR is the same: issuing time 5AM, valid as of 6AM.

I planned my route at 5:15AM, what was not in range of validity of both GAFOR. Pushing the new weather slider to 6AM, the Austrian GAFOR routes popped up as well

Nevertheless strange: Same range of validity for both GAFOR reports; one shows up, the other not

You said the reference altitude is the lowest altitude it's safe to fly along the route. From memory that is incorrect; the reference altitude is actually the highest terrain along the route. If you flew it at that altitude, there's a good chance you'd fly into terrain.

@Tim: You'r right: the reference altitude is the highest terrain along the route, including obstacles.