Store "Referal-Source" in URL

The overall goal is to automatically fulfill the "Referral Source" option of a contact form, even if the user has browsed the site for a while; and did not access the site from a UTM parameter campaign.

Method 1 (Maybe): I am familiar with UTM parameters, and essentially want to follow a similar format. Depending on the source of entry (to my website), the source would be stored in the url bar until they reach the contact form, then the url would simply be inserted behind the scenes of form submission

Method 2 (Maybe): Would it be a possibility to store the referral source in a cookie, and then insert behind the scenes of the form with a cookie output? Storing referrer URL in cookie

I am also open to better solutions

EDIT: I am thinking this is the solution for Method 2, but is this still the best method: https://wordpress.stackexchange.com/questions/166722/cookie-with-referral-url