Order status notification email customization

-- HikaShop version -- : 3.4.0
-- Joomla version -- : 3.8.7
-- PHP version -- : 5.6
-- Browser(s) name and version -- : Chrome newest

Hello,
I am using HikaShop Business 3.4.0.
How can i add a custom field to notification email. I mean that in the backend i modify the order and add a tracking number when the parcel is shipped. And i would like to have this tracking number attached in the email when i change the order status into "shipped".
I know that i have to edit order_status_notification_html.php but i have no idea how can i acces that specific custom field.

Thanks in advance

Thank You, I didn't notice that there was a such option. But that doesn't solve my issue, because i'd like to have this custom field shown just below the status title - like below:

Twoje zamówienie
Status Twojego zamówienia nr B3P6 został zmieniony na wysłane
Tracking Number: : 18035996393

Thank You, now it works great
Topic can be closed