Definition of CRS according to the proj library (API vs GUI)

[dcsa]

Hi,

We have successfully used the definition of a composed CRS (a horizontal projected CRS and a vertical CRS which respects a specific model of geoid) according to the proj library, in the Metashape API (I mean EPSG::CodeForHorizontalCrs+CodeForVerticalCrs).

We have tried to define this composed CRS in the GUI without success, as the results are different. To do so, we edited the projected CRS from the list of CRSs available in the interface, and selected:
Geographic CS: The one that uses the same datum but not projected.
Vertical CS: The CRS that defines the model of geoid that we want to use (previous download of the file in the metashape geoids folder).
Projection: the same projection used by the original projected CRS.
Units: those used by the original projected CRS .

Based on this experience, we would like to know if there is a way to select a composed CRS in the GUI according to the proj definition, avoiding the need to use the API, and why our definition in the interface does not return an equivalent result.

Thank you for any idea that can help us!