   <td>none</td>
      <td>A template function used to generate the contents of the tooltip. The function is called by the Timeline with an item data as the first argument, and must return HTML code, a string or a template as result. See section <a href="#Templates">Templates</a> for a detailed explanation.
      </td>
    </tr>
    <tr>
      <td>verticalScroll</td>
      <td>Boolean</td>
      <td><code>false</code></td>
      <td> Show a vertical scroll on the side of the group list and link it to the sc