My DNS as a record beginning with "google-site-verification=". It was probably done by me or someone else like a decade ago. Is there any way to tell what google login was used to create it? I assume not. If logged into a Google account, is there a list of domains that have been verified? Or is this a "fire and forget" type of verification. Should I just remove the existing verification and add a new one? What exactly does a verification accomplish? What might break if I remove the old one?
It was created for that Search Console property. If you no longer want to use that method you will need to verify account ownership with one of the other methods (GTM, GA, HTML Tag).
On Settings -> Users and permissions you may be able to see which user verified the propriety, if you have the right privileges.