Update: Märklin has fixed this issue with software version 2.5. Make sure RailControl Pro and the software on your CS3 are up-to-date to enjoy all your Track Diagrams. Read more
For unknown technical reasons, Control Desk-style diagrams don’t show up in the CS3 Web App and, consequently, are also missing in RailControl Pro. On the other hand, Panels are properly displayed in both applications.
Convert a Control Desk to a Panel
It is possible to convert a Control Desk to a Panel. As explained on page 35 of the Märklin CS3 User Manual. This way it’s possible to show the articles in the Track Diagram on RailControl Pro.
Related blog post: The curious case of Märklin CS3 Track Diagrams