I am adding custom data to a variable product. On the single product page I have a dropdown (woo controlled variation) and a javascript app that allows the user designs a poster. When the poster is done it is save to a database and an id is returned. I then save the id in the custom field and the customised product can be added to the cart. I display the id on the cart item and on the order as well. But if I want to edit the item after I have added it to the cart (clicking the item in the cart) i only get the variation value (as part of the GET url)

It is more than likely that a customer could have two (or more) items in cart from the same variable product with the same selected variation (but with different custom values). These items would have the exact same url and no way for me to differentiate between them.

I would like to add the value of my custom field to the url.

Is there a way to do that?
Or does anyone have a different approach to solve this problem?
Thanks in advance