Updating Anonymous contacts

Your software
My Mautic version is:
My PHP version is:
My Database type and version is:

Your problem
My problem is: How do you update anonymous contacts?
I would like to take the details from the anonymous contacts (ip address, referrer etc) and update the contact fields. Ideally I want to take the ip address and add it to my ip address field. I want to do this as I update contacts when I get a sale in shopify and use the ip address metadata as a unique identifier (and therefore merge the contacts)

I do this as I can’t seem to find a way for shopify to pass the cookie over in the contact update process via Zapier.

So the overarching question is - how do you update anonymous contacts with, in this case a unique identifier (ip address).

Thank you