Hey @WesleyMaik, how’s it going?
If I needed to add a variable to all items in the cart, I think the best approach would be to follow the Attachments Documentation to create the attachment and enable it for the desired SKUs, and finally create a script to be triggered when the Buy Button is clicked and add the item with the attachment to the OrderForm, following the idea in this other post here that shows an example of how to add an attachment to an item:
This way, a new field for the product would only be necessary if you need to display this information on the PDP or apply some kind of filter — otherwise it wouldn’t be needed.
If I didn’t quite understand your scenario, feel free to share more about the solution you’re building and how it will be used.
Cheers!