Can you add tags via hidden form fields?

I’m using Swipepages to build out some landers and their Aweber integration only lets you specify which list to add subscribers to, and map your form fields to that list.

There is no mechanism on their side to “tag” new additions to the list - and their support doesn’t really understand what I mean when I ask for it.

But we can add custom and hidden fields over there, so could I just add hidden fields that would have the same effect as tagging the subscribers as they get added?