Can I include hidden fields from froms on other platforms?

If I have an Instapage form (meaning a form BY the platform Instapage, not a form embedded on it), can I still use the ?session=email tag for users to have the ability to save their progress?

I am not sure if I understand your query correctly. Are you referring to the form designed within the Instapage website and not from JotForm? If so, unfortunately, we cannot provide any assistance with respect to the forms other than JotForm and you may need to check with the respective product support for any questions that you may have.

Hope this information helps! Let us know if you are referring something different. We will be happy to assist.