This plugin adds a universal top menu among WordPress sister websites.

iamraymund

Menu Organizer

A simple plugin to organize your admin menus

Kevon Adonis

This plugin adds a universal top menu among WordPress sister websites. 
Administrators may manage menus from one central location (a master site) and use the client plugin (pending) on remaining sites to display the menus. 
Or simply add the master menu to all sites that needs the top menu. 
Create as many menus as you like. If you are using the client plugin to display the menus 
on sisters sites you first need to add that site to the list of menus first on the master site. 
After creating your menus choose from ten (10) color themes under settings and you’re all set to go.
Please feel free to request more themes and features (email @ kevonadonis.com )

Alternatives to WP Group Menu

Top alternatives