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remove_filter( 'nav_menu_description', 'strip_tags' );
function containertraders_setup_nav_menu_item( $menu_item ) {
    if ( isset( $menu_item->post_type ) ) {
        if ( 'nav_menu_item' == $menu_item->post_type ) {
            $menu_item->description = apply_filters( 'nav_menu_description', $menu_item->post_content );
        }
    }
    return $menu_item;
}
add_filter( 'wp_setup_nav_menu_item', 'containertraders_setup_nav_menu_item' );