Queries regarding MegaMenu Navigation on Sharepoint Site

Shweta Tuli Assuming that you mean a modern site, here are the answers:

1. The navigation items are entered in manually by the owner of the site.

2. You can have up to three levels in the hierarchy. If you are using a megamenu, you should use all three levels because the user experience is optimized for that experience. If you only need two levels, the cascading style is a better choice.

3. You cannot set a target audience yet, but that feature is definitely planned.

4. Mega menu is site-specific. However, if you make a site a hub site, then the mega menu can be shared among all the modern sites associated to the hub. Just for fun, I tried creating a modern sub-site from a communication site and the megamenu navigation doesn't appear to inherit even though I set it up to do so. Sub-sites are not the preferred structure for modern architectures so I would not assume that mega menus on modern sites would show on the subsites (which can only be team sites).

5. Mega menus are limited to sites that have top navigation. It wouldn't be a good user experience to have a mega menu in left navigation. They work great on communication sites and if you want a mega menu experience on a team site, you would need to make the team site a hub site. Since hub sites have top navigation, you could create a mega menu experience for the hub site itself as well as all the sites associated to that hub.

Take a look at Planning Navigation for the Modern SharePoint Experience to learn more: https://docs.microsoft.com/en-gb/sharepoint/plan-navigation-modern-experience.