Indeed, the feature that is missing is the ability to reuse pieces of an already developed robot and import them into the new robot, and attach that to the desired location / step in the robot.  It would be a kind of import or extend option. 

A similar option would be useful for the object model.  I am a relatively new user of the product, but have worked with other similar ones.  I have not yet found an easy / obvious way to achieve this essential functionalities.

... just adding my voice to a worthy cause -)