hey I don’t know if anyone’s still looking for a solution to this.
I wrote a how to + shared the code for creating 2 step forms.
However with this method you can chain any amount of forms if you want, it’s just nicer to split the code into neat functions rather than what is done in the how-to.
hopefully this helps someone!
how-to:
https://hyper-typed-marketing.mailchimpsites.com/growth-multistep-forms-hubspot
code: Two-Step form in HubSpot · GitHub
P.S. this works without hiccups except that… completing two step form counts as.. two form submissions 
Edit: I made a multi step generator so nobody has to painfully copy paste code. see other reply for more details: