<div class="treeview">

  <ul>

       <li class="d-flex flex-row">

          <a href="#"> Root</a> 

          <div class="dropdown mx-4">

          <button

            class="btn btn-primary btn-sm dropdown-toggle"

            type="button"

​

            data-mdb-toggle="dropdown"

            aria-expanded="false"

          >

​

          </button>

          <ul class="dropdown-menu"  >

            <li><a class="dropdown-item" href="#">Action</a></li>

            <li><a class="dropdown-item" href="#">Another action</a></li>

            <li><a class="dropdown-item" href="#">Something else here</a></li>

          </ul>

       </div> 

        <ul>

            <li class="d-flex flex-row">child-1</li>

            <li class="d-flex flex-row">child-2</li>

        </ul>

     </li> 

  </ul> 

</div>

dropdown-toggle {

  padding: 2px;

  width: 10px;

}

​