     alternateAlignment: go.TreeAlignment.Bus,
        alternateNodeSpacing: 20
      }),
      'undoManager.isEnabled': true // enable undo & redo
    });

    // when the document is modified, add a "*" to the title and enable the "Save" 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 