The TreeView widget seems to work well as long as the TreeItem 'data' field is a string. However, when I use a CustomNode for the data field the expand/collapse graphic disappears from that TreeItem. My custom node is nothing special - just an HBox that contains a toggle button, a label, and a text field.

  var tc = TreeView {
                showRoot: false;
                root: TreeItem {
                    data: "never see this";
                    children: [
                        TreeItem {
                            data: "here is question 1"
                            children: [
                                TreeItem {
                                    data: tInteger; // this is my custom node
                                    children: [
                                        TreeItem {
                                            data: "here is question 1.1.1";
                                        }
                                    ];
                                }
                            ];
                        },
                    ]
                }
            }