Many professional tools have a strong GUI/Engine separation, AutoCAD famously used Lisp, and one could see and modify commands that were being dumped into the application REPL in real time.

Many applications on the Amiga had an ARexx Port that allowed scripts to drive all the same actions as the user.

http://docs.autodesk.com/ACDMAC/2013/ENU/PDFs/acdmac_2013_au...

http://www.pjhutchison.org/tutorial/arexx.html