How can I add one Node to another

[marcusMintchip]

Trying to achieve a UI that faces adding one Node to another Node,there's addNode(GModel,GNode) function ,so I've tried using node.getSubGraph() to get GModel and and another GNode but it couldn't work, Can anyone help me about this UI construction?

Here's the code I tried in Demo code
createContent.md

[marcusMintchip]

` private void createContent() {

    header.getStyleClass().setAll(STYLE_CLASS_HEADER);
    header.setAlignment(Pos.CENTER);

    title.getStyleClass().setAll(STYLE_CLASS_TITLE);

    final Region filler = new Region();
    HBox.setHgrow(filler, Priority.ALWAYS);

    filler.setOnMouseClicked(mouseEvent -> {
        System.out.println("region clicked");
        GModel model = GraphFactory.eINSTANCE.createGModel();
        getNode().setSubgraph(model);
        GNode node = GraphFactory.eINSTANCE.createGNode();
        Commands.addNode(getNode().getSubgraph(), node);

// HBox subHeader = new HBox();
// subHeader.getStyleClass().setAll(STYLE_CLASS_HEADER);
// subHeader.setAlignment(Pos.CENTER);
// Label subTitle = new Label();
// subTitle.getStyleClass().setAll(STYLE_CLASS_TITLE);
// subTitle.setText("subTitle"+getNode().getId());
// Region subFiller = new Region();
// HBox.setHgrow(filler,Priority.ALWAYS);
// Button close = new Button();
// close.getStyleClass().setAll(STYLE_CLASS_BUTTON);
// subHeader.getChildren().addAll(subTitle,subFiller,close);
// contentRoot.getChildren().addAll(subHeader);
});

    final Button closeButton = new Button();
    closeButton.getStyleClass().setAll(STYLE_CLASS_BUTTON);

    header.getChildren().addAll(title, filler, closeButton);
    contentRoot.getChildren().add(header);
    getRoot().getChildren().add(contentRoot);

    closeButton.setGraphic(AwesomeIcon.TIMES.node());
    closeButton.setCursor(Cursor.DEFAULT);
    closeButton.setOnAction(event -> Commands.removeNode(getGraphEditor().getModel(), getNode()));

    contentRoot.minWidthProperty().bind(getRoot().widthProperty());
    contentRoot.prefWidthProperty().bind(getRoot().widthProperty());
    contentRoot.maxWidthProperty().bind(getRoot().widthProperty());
    contentRoot.minHeightProperty().bind(getRoot().heightProperty());
    contentRoot.prefHeightProperty().bind(getRoot().heightProperty());
    contentRoot.maxHeightProperty().bind(getRoot().heightProperty());

    contentRoot.setLayoutX(BORDER_WIDTH);
    contentRoot.setLayoutY(BORDER_WIDTH);

    contentRoot.getStyleClass().setAll(STYLE_CLASS_BACKGROUND);
}`