Is it possible to add non-Marketo fields in a form? For example, creating a form to register for an event and want to add a field to select the correct event on a roadshow. Is this possible?
You can definitely do this. You will need a custom Marketo only field. See this walkthrough: http://www.marketingrockstarguides.com/setup-recurring-webinars-in-marketo-1479/