It has been on my list for a very long time to get STACK and GeoGebra working together, so that the configuration of a diagram can become part of the answer.
Thanks to Andreas Schekel we now have a working example, which I've posted here: https://stack.maths.ed.ac.uk/demo/course/view.php?id=16
This is a great opportunity to contribute something back to STACK without necessarily changing the STACK code (although I anticipate for really tight integration we can do this as needed). If you are interested in helping, please drop me an email at C.J.Sangwin@ed.ac.uk.
One contribution which would be very valuable would be to send me some example questions you'd like to automate. To what uses would you put GeoGebra. Compelling examples have always driven the development of STACK, and this is a good time to collect some using Geogebra.