After searching in vain for how to change the default 'submit a request' form at the top of the Guide pages for Guide viewers who are not logged in, I thought I'd share the actual answer in the hopes that this will show up when people search the community site:
- First, this is not a page that is accessible or configurable from Support configuration using 'Ticket Forms' or 'Ticket Fields' as other support articles and posts suggest. I upgraded my Support license so that I could modify these forms and fields only to find that the 'Submit a request' form page is not (directly) related to those features.
- You must be on at least a Professional Plan for Guide to gain access to the 'Edit Code' function.
- Once you're on the Professional or higher plan, you will find the 'Edit Code' button to access this form under the Guide's 'Customize Theme' section. Note the link is not in the list of customization categories - it is placed in the lower right corner next to the publish button.
- When you are on the edit code page, you will see the form in the list titled, "new_request_page.hbs".
- You can then edit this form using HTML to add content or modify in other ways. Note that not all HTML is supported.
It is also worth noting that there is at least one official ZenDesk support article that shows that you can edit forms and fields in the Support configuration with a 'Professional' license for Support and this can be misleading. In order to access full form(s) and field configuration you need something call the 'Productivity Add-On' which is noted in some but not all related support articles.

Hey Yvonne,
If you're trying to add more ticket fields to your Submit a Request page, you'll want to take a look at this article: Adding custom fields to your tickets and support request form
Let me know if that's not what you're looking for!