iRhino3D WIP (8.0.23299 (11.2.1) - October 27) available via Testflight supports copy and pasting between iRhino and Rhino for Mac using Apple’s Universal Clipboard functionality.
This is an unfinished feature with some known issues and many unknown ones. Please report here if you find an issue 
For serious work, use the Appstore version of iRhino3D.