Here is a small snippet you can copy and paste to your child theme to add a shortcode <wpslash_voucher_courier_tracking> to WooSMS .

add_action('woosms_extends_variables', 'wpslash_add_tracking_variable_to_woosms', 10, 2);

function wpslash_add_tracking_variable_to_woosms($variables, $database)
  $variables->set('wpslash_voucher_courier_tracking', $row->wpslash_voucher_courier_tracking);


Note: If for any reason you cannot add it to yourself , feel free to open a ticket and we will take of adding this code to your child theme!