If you are not using the Advanced Orders Display Text you could
use that. However, if you are can make use of hidden variants to record
this information.
First create a variant under Inventory, Variant Templates.
Then go to the Product Details page and scroll to the Variants area. Next to Select Variant, find the Variant Template and Add Selected.
Unhide the variant if it is hidden and under the Variant Column, add the information you want.
You can then hide that information again. This means the Variant will only be seen by you for that product.
First create a variant under Inventory, Variant Templates.
Then go to the Product Details page and scroll to the Variants area. Next to Select Variant, find the Variant Template and Add Selected.
Unhide the variant if it is hidden and under the Variant Column, add the information you want.
You can then hide that information again. This means the Variant will only be seen by you for that product.