Answer:
This can be done relatively easily using the tools integrated in RFEM. The following video shows the steps required to divide a free-standing double-curved surface into four quadrants. Further information can be found in the description below.
To do this, you need to create a user-defined coordinate system containing three points that define the desired section plane.
Then you can align the working plane here.
And select the “Divide by intersections” option in the shortcut menu of the surfaces.