I think this would only be possible in Webflow using custom code. Not sure about a 3rd party tool, maybe you could look at using conditional logic instead of adding fields and use something like Typeform?
I know it’s a year-old thread however I need to do the same thing, I’m very new at Webflow so I don’t know how to use the custom code. Is this achievable within Webflow or do I have to use a third party tool like Jotform?