Alternative to Dynamic Cookie Names

@m_hutley Can we please take this step by step, because I try to get my head arrount this without success sofar.

First step. Someone subsribes to the mailing list (The first Cookie is set:

Cookies.set('mailinglist_popup', 'yes', { expires: 1000 });

The person receives a thank you email with a link in order to confirm there subsription Clicking the link will bring them to a thank you page where a second Cookie is set:

Cookies.set('mailinglist_active', 'yes', { expires: 1000 });

And this is the point where I am loosing you. So any input from here would be more than welcome.

Thank you in advance