Highlight custom post type menu under WooCommerce

custom-post-type-menu-woocommerce

// Highlight custom post type menu registered under WooCommerce (sub menu)
add_action( 'admin_head', 'menu_highlight' );
function menu_highlight() {

    global $parent_file, $submenu_file, $post_type;

    if ( $post_type == 'custom_post_type' ) {
        // We change $submenu_file to current $parent_file,
        // so the $submenu_file for post type add and edit screen is same.
        $submenu_file = $parent_file;

        // Then, we change $parent_file to woocommerce,
        // so when we navigate to post type add or edit screen,
        // WooCommerce admin menu will be opened.
        $parent_file = 'woocommerce';
    }

}