along asks button buyer cart common customer edit feature field form modify page product show thank-you variants

I'd like to add a page in my cart or on the same page that asks where the customer heard of the product. Is this possible? If not what would be the best way to ask?

You can use our variants feature to have such a field for "each" product along with it's ADD TO CART button. However, it's not possible to edit the cart to have a common field.

Alternatively, you can modify the "thank you" page to include a form where you show this question to buyer.