WordPress Mega Menu can work without Visual Composer plugin. But if you installed Visual Composer plugin you can build any menu easily, just turn on Visual Composer editor for WordPress Mega Menu.
1 – Goto Visual Composer menu.
2 – Choose “Custom” in “Post types” dropdown and check the “zanmenu” checkbox in “Role Magager” tab.
3 – Save change. Now you can edit menu content with Visual Composer.