Typically our code will convert rhino/grasshopper entities into the most appropriate IFC class that is similar.
We don’t have an explicit composite curve component (but if it’s critical we can add it), but the convert curve component will take a rhino polycurve and generate a composite curve (there is a similar but more efficient alternative in IFC4 or newer).
Here is an example, does that achieve what you need?
250526 composite curve.gh (7.1 KB)
Cheers,
Jon