I would like to add some additional topics to the mega menu, especially sub-menu items contained within the About Us and adding additional parent level topics. Using NopCommerce 3.3
You can do this, but you have to be a little familiar with html and css.
If you want to have to have top level topics you have to go to this file:
and find this helper: @helper RenderMegaMenu(bool isMegaMenuResponsive)
inside it, you can add your top level links and they can be as many as you want with the following structure:
<a href="yourLinkToTopic">Your Topic Title</a>
To achieve About Us sub-menus you must be familiar with Razor and it is a customization that is out of our support line.
Best Regards !