I have looked at some tutorials and have built some small GUI with TornadoFX, but all of the (small or easily understandable) examples that I can find for the topic are projects where the user is the main source of change in the program flow. Like a window that does nothing on its own and when a button is pressed, it quicly does some small thing and then goes back to waiting.
All my use cases are of the opposite kind: There is some complicated process running in the backend background and the GUI is just a kind of dashboard to show the user what is happening.