You can use a different menu for the top and sidebar menus.
The recommended setup is to use the top menu for your informational links e.g. Home, About, Contact etc. and use the sidebar menu to display you store collections.
Creating menus and links isn’t part of the theme code. It’s part of the Shopify admin area. Please see this Shopify document for more details on working with menus.
Once you’ve created your menus, you can use the theme settings to define where they appear.
The Top Menu
Click “Customize” next to the theme name then open the “Header” section and you’ll find an option to select the menu for that section.
The Sidebar Menu
Click “Customize” next to the theme name then open the “Sidebar” section and you’ll find an option to select the menu for that section.