Run this code - expected that the accordion should not participate in focus traversing
@Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("Hello World!");
        Button btn = new Button();
        btn.setText("Say 'Hello World'");
        btn.setOnAction(new EventHandler<ActionEvent>() {

            @Override
            public void handle(ActionEvent event) {
                System.out.println("Hello World!");
            }
        });
        Accordion accordion = new Accordion();
        TitledPane pane = new TitledPane("Title 1", new Button("Ok"));
        accordion.getPanes().add(pane);
        accordion.setFocusTraversable(false);
        HBox root = new HBox(15);
        root.getChildren().addAll(accordion, btn);
        primaryStage.setScene(new Scene(root, 300, 250));
        primaryStage.show();
    }