Unfortunately, I couldn't make it to the AERO in Friedrichshafen due to a very busy schedule at my work. I even forgot to mention it before and forgot about all my other open topics. My appologies for that.
I've figured out that "AirNavPro" (ANP) displays all the Approach frequencies for the German (non-CTR) TMAs, like Langen Radar "118,750" and "135,350" for Cologne/Bonn. It would be great to have this information also in SkyDemon, so pilots can contact the appropriate ATC-unit directly, instead of using FIS, which costs time and decrease the chances of a clearance. Did the DFS say something about this already to you guys? The frequencies are mentioned within the IFR SID and STAR-charts.
Furthermore, I've found out that SkyDemon does not display any frequency for general class C in Switzerland, which would be very usefull to get an "on op" clearance for the Alps. For the western part, this would be "Geneva Delta" on 119,175 and for the eastern part, this would be "Zurich Delta" on 119,225. The boundaries between Zurich and Geneva for Delta are the same as for Information (FIS).