You can change the Semibox layout very easily by adding the below attribute to the body tag in the index.html file.

data-layout="semibox"

How to add new menu items/change menu items?

To add, change or remove menu items from the left side navigation, simply edit in file index.html. The change would reflect in all the HTML files automatically. We are using gulp which would take care of including the index.html file content in all HTML pages.