Code:

    
    @Override
    public void start(Stage stage) throws Exception {
        Accordion acc = new Accordion();
        
        TitledPane pane1 = new TitledPane();
        pane1.setText("Some text");
        pane1.setGraphic(new Label("Node"));
        pane1.setContent(new Button("Some button"));
        acc.getPanes().addAll(pane1);
        
        Slider slider = new Slider(0, 100, 50);
        slider.valueProperty().bindBidirectional(pane1.graphicTextGapProperty());
        slider.setShowTickLabels(true);
        slider.setShowTickMarks(true);
        
        VBox pane = new VBox();
        pane.getChildren().addAll(acc, slider);
        Scene scene = new Scene(pane, 300, 700);
        stage.setScene(scene);
        stage.show();
    }

Move slider.