In the Netherlands we have different coordinatesystems for 2D (EPSG:28992) and 3D (EPSG:7415). The last one is a combination of EPSG:28992+EPSG:5709. When using models I would like to have the option for different coordinatesystems added to different models in the same DGN. Or when adding coordinatesystems to models, I only see 2D coordinatesystem when in a 2D model ór 3D coordinatesystems, when using 3D models.
Thank you for submitting this idea.
MicroStation fully supports having multiple models (2D and 3D) within a single DGN file. For more details, please refer to the Models section in the MicroStation documentation:
https://docs.bentley.com/LiveContent/web/MicroStation-v2025.0.1/Help/en/topics/122971/GUID-B8D59805-6357-AE9F-641E-9EA5C961F631.html
The coordinate system library does not include combined vertical and horizontal GCS. You need to first select the horizontal coordinate system, and once that is selected, choose the appropriate vertical coordinate system from the list in the Vertical Coordinate System section.
NAP2018 refers to EPSG:5709.
I hope this information is helpful.