Answer:
As of version RFEM 6.02.0071, the RSECTION cross-section is imported into RFEM through the Dlubal Center (Image 01).
In order to access the file in the Dlubal Center, the RSECTION file can be saved in the Dlubal folder (Image 02). Make sure the file is saved inside the “examples” folder.
The file can also be saved in a different location by choosing the option to Add existing project and selecting the relevant folder (Image 03). Do not use the Create new project option.
The RSECTION file can then be found under Models in the "Projects" folder (Image 01).