          <li class="nav-item" data-level="3"><a href="#example-9-vertical-sliders" class="nav-link">Example 9: Vertical sliders</a>
              <ul class="nav flex-column">
              </ul>
            </li>
            <li class="nav-item" data-level="3"><a href="#example-10-knobs-instead-of-sliders" class="nav-link">Example 10: Knobs instead of sliders</a>
              <ul class="nav flex-column">
              </ul>
            </li>
            <li class="nav-item" data-level="3"><a href="#exampl