I can place a new menu item to the end of the root level menu items by using this:
function bv_show_book_online_menu_item($items, $args) {
if(bv_can_book_online()) {
if($args->theme_location == 'main-menu') {
$items .= '<li><a href="/book/">Book Online</a></li>';
}
}
return $items;
}
add_filter('wp_nav_menu_items','bv_show_book_online_menu_item', 10, 2);
But how can I actually insert the item in any place I want? I actually want to place it in the middle of submenu like this:
Menu Item
Submenu Item
Submenu Item
<-- Insert new submenu item -->
Submenu Item
Submenu Item
Menu Item
Submenu Item
Submenu Item
Submenu Item
etc