Add menu page on multisite

I believe you’re looking for the network_admin_menu hook.

Here’s how you’d use it:

add_action('network_admin_menu', 'function_name');
function function_name() {
    add_menu_page( 
        "page_title", 
        "menu_title", 
        'capability', 
        'menu_slug', 
        'function_callback' 
    );  
}