@LongNguyen, thanks to @stevebaer, we have a method of calling into the GH dll which Rhino loads. You can check out Sample 2 to see an example of utilizing this functionality.
Specifically, it uses
- Rhino.Runtime.HostUtils.RegisterNamedCallback() (Reference in Sample 2)
- Rhino.Runtime.HostUtils.ExecuteNamedCallback() (Reference in Sample 2)