Empire comes with the option to add up to 10 additional menus in the Sidebar.
Enable the Sidebar navigation
To enable this feature, navigate to a collection page in the theme editor. In the left-side settings, open Collection pages then select Show sidebar.
To add a menu, click Add menu or one of the existing menu blocks, then select the menu you want to display.
Menu depth
Customize the depth of your menus from the Menu depth visibility slider.
The easiest way to add a new menu to your store is by adding a dropdown menu to one of your pre-existing links in the main menu. For example, you may have a main menu link to "Our Process". If you want to go into depth about that topic, you could create a multi-level menu, something like this:
You might even want to take things a step further, with separate pages for each of your suppliers and factories, for example.
To create a multi-level menu, navigate to Online store > Navigation. Choose an existing link in the main menu to "drop down" from, then add a new link to the main menu to use as the name from the new dropdown. In this example, we're using the "Our Process" menu item.
Then create a new menu with that shared name, and enter your desired menu items. Like so:
Then navigate back to the theme editor (Collection pages > Menu depth) and specify how many tiers you would like to display. Empire supports up to three tiers.