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 ?

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