Left-side sub-menu

If you plan to have third-level pages, a menu to access them must appear in the left column of each parent second-level page:

  1. Modules > scroll down to Other; check Menu Block > Save
  2. Structure > Blocks > Add menu Block > Block title: <none> > Menu: Main Menu > Starting Level: 2nd > Region setting: Sidebar first > Save
  3. Add the following media query to hide the submenu on mobile:
    1. Configuration > CSS Injector > open your existing CSS core style sheet.
    2. Add the following rule:
      @media screen and (max-width: 768px) {
      .menu-level-2 {
      display: none;
    3. Be sure you include all the brackets: }.