button
    myDiagram.addDiagramListener('Modified', (e) => {
      const button = document.getElementById('SaveButton');
      if (button) button.disabled = !myDiagram.isModified;
      const idx = document.title.indexOf('*');
      if (myDiagram.isModified) {
        if (idx < 0) document.title += '*';
      } else {
        if (idx >= 0) document.title = document.title.slice(0, idx);
      }
    });

    myDiagram.nodeTemplateMap.add(
      'Comment',
      new go.Node()
        .bindTwoWay('location', 'l