Adding fields to email templates (not attachments)

We are currently using a sale workflow to update our B2B customers with a tracking number.

The current flow sends an email to our customers with the box label attached which includes the tracking.

I want to update the actual email to include the tracking (instead of having to click the box label attachment to access the tracking).

I would very much appreciate a feature to add the «TrackingURL» directly in an email (instead of an attachment).