Discount amount to show in email and/or export

When a discount code is applied in the cart, the text appears in the item something like "You've saved $$ on this item". That's great. Is there any way to capture that amount so that it can be shown in the email and export templates and/or in the external submittal?

There's an undocumented specialcode that could be of use for you.
It's [ORD_MATCH_EXTVARS_DESC] and technically would be ORDER: Descriptions of matching external variables rules, if any.

Honestly I do not remember why it is undocumented, so you can try using it and let me know if it just works as expected.
In that case I'd dimple make that "official"