Hi stephane-lavoisard,
At the moment, you can use the Custom module with the following HTML code to create the menu item on the topbar:
<ul class="nav navbar-nav ">
<li class="nav-item"><a href="/cp-montessori" class="nav-link"><span><span class="menu-item-title">Montessori</span></span></a></li>
<li class="nav-item"><a href="/cp-switch" class="nav-link"><span><span class="menu-item-title">Switch</span></span></a></li>
</ul>
I have helped you create the Custom module, you can check your site now.