Hey, it took me a while to convince myself that you hadn't found a cool new way to do multi-scene JavaFX, but sadly, no.
So, I think you need a whole new approach to doing this. To see one way that I developed, look at this GitHub repo
. You'll need to look at the pre-javafx-11 branch unless you are using JavaFX 11.
You can also search GitHub and find other ways to do this.