Grouping in CAD before Exporting to STL file

I would like to somehow organize my model in Rhino3D so that I can export and import into Caedium with the model faces already in groups.

Is that possible?

Group import

Faces that form separate volumes are implicitly groups, i.e., a volume. Individual STL files are just lumps of facets that are supposed to form closed volumes, but often do not.

You could export each group as a separate file, then in Caedium form groups of these new faces after each import.

Avoid using STL

Also, if you have the choice, I suggest you avoid using STL given its ambiguous topology and its inherent inaccuracy. STEP (.stp) is a much superior exchange format.