You have the ability to enable expandable menus in all of the side navigation layouts. An expandable menu is simply a section of pages you have categorized in your navigation menu that is able to be viewed by a click of the mouse.
Note: These options are only available with side navigation layouts.
1. To start, you will want to create and organize your sitemap in Content by adding new pages or Navigation Items. See this article for steps on adding a secondary menu (only pages designated as secondary pages will be included in the expanded area).
2. Select the Design tool in the gray navigation bar, then on the right-hand side of the preview, under Sitewide, select Navigation.
3. Scroll down the design options and open the Expandable Menus area.
4. You will see an area for Sub-Navigation. Click the drop-down to show your options.
Select "Expand to click": choosing this option will place all secondary pages into collapsed dropdown areas that can be expanded via a click in the navigation menu.
To elaborate, "Expand on click" will enable the drop-down option in your navigation menu. Selecting "Always expand" will keep your navigation in it's normal view where all pages/secondary pages are shown in the navigation menu. Make your design changes in this area, then select Save to finish.
5. You will also see options to style the navigation text color and the selected text color(current/selected page), along with the background color.
6. Select the Save and Publish button to take your changes live!