Here’s a link to the original thread this came from:
https://ogrforum.com/...collectors-quarterly
As Jan said, the software is RR-Track and the track is Lionel O, there’s even a movie in the thread. In SCARM, the 45° crossing is at the bottom of the Lionel O library, #5545. If you try to recreate it in software, note that the design includes cut tracks. RR-Track doesn’t have a free trial version, so I suggest using SCARM. I don’t have RailModeler Pro, so I can’t help there.
However, you mentioned “standard” gauge, did you really mean that? SCARM has libraries for Standard Gauge (1:26.6) as well as “S” Gauge (1:64). The S Gauge library includes tracks for American Flyer (discontinued), American Models, FasTracks, GarGraves, Lionel and MTH. The only ones that have a 45° crossing are FasTracks (templates) and Lionel FT (American FastTracks). TrainZ sells some tracks, but I don’t know if that’s what you really mean.
https://www.trainz.com/collect...-45-degree-crossover