This action is used to add extra submenus and menu options to the network admin panel's menu structure. The network admin panel is only seen by a super admin in a multisite installation.
The function associated with this action runs after the basic network admin panel menu structure is in place. For example, the function might call add_submenu_page to add a sub menu page.
<?php
add_action('network_admin_menu', 'add_network_menu_1234');
function add_network_menu_1234() {
add_menu_page( "page_title", "menu_title", 'capability', 'menu_slug', 'add_network_menu_1234_cb');
}
?>
Where "add_network_menu_1234_cb" is the name of the function to be called.