We're trying to get some unique ID for anonymous users, but I don't see any such id in the Session object which we get via the Environment component of Extensibility API. Is there a way to identify an anonymous user via some unique ID? (SC 2020.2.3)

I have the same issue. At the moment, the only option I can see is to fetch the NLVisitorId cookie value, which is currently not HttpOnly. I'm not overly happy about doing this though, as if they change it to HttpOnly it's likely to cause major issues. I'd be a lot happier if we had more options to get/set customer and session fields.

I would use the UserProfile component. An anonymous user can be determined if

isloggedin

and

isrecognized

both return false

Identifying whether a user is anonymous or not is not a problem (we do use the method you suggested for that), but we want to identify the particular anonymous individual, preferably via some unique ID (ex: '1234' for Anonymous User 1, '2345' for Anonymous User 2). I couldn't find any method in Extensibility API that can give me such a value.

Well AFAIK the only things we have are the cookies, as Dominic says

Okay, I will try to incorporate those for now then.