Ah! Both answers are very good. I could never get -extend to work before but now I do (I didn't realize that you should call ad_form several times, without -extend in the first call, to extend a form).
Jeff's code works!! 😊 What beats me is why you must call [list] for the outermost two lists and can't just use {} instead. ({} does not work, I tried).
Isn't {} = [list] ?
