I have my controller with the tips you said but the borders are still not corrected. When I go to initialize my panel to set the background the command:

yourPane.setBackground(new Background(new BackgroundFill(Color.TRANSPARENT, CornerRadii.EMPTY, Insets.EMPTY)));

I get error in Insets.EMPTY, I tried to fix it like this but I still don't see the borders corrected.

void initialize() { confirmDialog.setBackground(new Background(new BackgroundFill(Color.TRANSPARENT, CornerRadii.EMPTY, new Insets(0)))); }