openproject/app/assets/javascripts/specific/main_menu.js.erb

<% environment.context_class.instance_eval { include ApplicationHelper } %>

jQuery(document).ready(function($) {
  // rejigger the main-menu sub-menu functionality.
  $("#main-menu .toggler").remove(); // remove the togglers so they're inserted properly later.

  $("#main-menu li:has(ul) > a").not("ul ul a")
    // 1. unbind the current click functions
    .unbind("click")
    // 2. wrap each in a span that we'll use for the new click element
    .wrapInner("<span class='toggle-follow ellipsis'></span>")
    // 3. reinsert the <span class="toggler"> so that it sits outside of the above
    .append('<%= icon_wrapper("toggler icon6 icon-arrow-right5-2", I18n.t("description_menu_item_toggle")) %>')
    // 4. attach a new click function that will follow the link if you clicked on the span itself and toggle if not
    .click(function(event) {
      if ($(event.target).hasClass("toggler") ) {
                          var menuParent = $(this).toggleClass("open").parent().find("ul").not("ul ul ul");
                          menuParent.mySlide();
                          if ($(this).hasClass("open")) {
                            menuParent.find("li > a:first").focus();
                          }
                        return false;
                      }
    });
});