The dynamic content of email notifications (if it exists) is added to the message below the main text (default location).
Alternatively, you can insert it in a different location within the notification via the variable %dynamic_message%.
To change the dynamic content of a notification:
Open the email notifications list in your store's Admin area (Store Setup -> Email Notifications) and proceed to the notification details page as described in Editing the Texts of Email Notifications.
Locate the "Dynamic message" field and click the "Edit" button opposite it.
This opens a dynamic message editor in a new tab.
In case there is no dynamic content embedded, you will see the following message:
In the above notification, the dynamic message is empty. If you need to use specific TWIG code, use the template tree on the left-hand side of the screen to choose the TWIG file you require. For plain text, we recommend using the WYSIWYG editor on the "Edit notification" page.
Click either on a file path to the left or double-click on a highlighted content to the right.
This opens a new tab with a twig file code.
Edit the twig code the way you need it.
Click Save changes.