I developed a FreeCAD workbench for converting CAD files to GDML a few years ago. It works nicely and has been used in many projects. I would like to share it with the geant4 community.
Its source code can be found on the github repo : GitHub - drhlxiao/g4cad: A freecad plugin which allows exporting CAD models to geant4 gdml files
If you have any questions, comments, or suggestions, please let me know.