The question is rather short: Why can't one copy/paste - duplicate the GUI elements on the form. 
Isn't it a little silly not to be able to have that rather necessary feature?

I (or any other Joe) currently have to implement more that 18 text fields that should differ only by the names, and have
to type every custom parameter in  - for every field. 

I would also be very happy to read the usability study whose results you have followed and removed the most common
features (I know that it can be complicated to implement the code generator under the surface) that any serious editing
environment does not even mention in the feature list.

Cheers
George Feketitsch