Powerpoint XML修改-将子项添加到UI中的按钮

我有以下代码：

<group id="upperTriangles" label="Upper Triangles">
<button id="addInfo" label="Add Info" image="AddInfo" size="large" onAction="AddInfo" />
<button id="risk" label="Risk" image="Risk" size="large" onAction="Risk" />
<button id="updated" label="Updated" image="Updated" size="large" onAction="Updated" />
</group>

这将在UI中生成3个按钮，分别称为AddInfo、Risk和Update

现在，假设我希望Risk按钮本身不做任何事情，而是显示一个包含多个子项的菜单，这些子项是按钮，如下所示：

如何实现这一点？

按钮下拉列表：

<menu
  id="Menu"
  image="Logo32"
  size="large"
  label="General"
  showImage="true"
  screentip="Main menu"
  supertip="General functionality">
  <button
    id="ButtonKB"
    image="KB16"
    label="Knowledge Base"
    screentip="Knowledge Base"
    supertip="Open the Knowledge Base"
    showImage="true"
    showLabel="true"
    onAction="Open_Knowledge_Base"/>
  <button
    id="ButtonLibrary"
    imageMso="AccessTableIssues"
    label="Library"
    screentip="Library"
    supertip="Open the Library"
    showImage="true"
    showLabel="true"
    onAction="Open_Library"/>
  <button
    id="ButtonBiographies"
    imageMso="AccessTableContacts"
    label="Biographies"
    screentip="Partner Biographies"
    supertip="Open Biography Library"
    showImage="true"
    showLabel="true"
    onAction="Open_Biographies"/>
</menu>