Hi there,
being able to mark certain fields as ‘hidden’ in the legacy form editor is a great feature whicih I would love to also see in the new beta editor for forms!
Status: Idea Submitted
Hidden fields with UTM data are a requirement for the way our reporting is set up. I will not be able to implement any forms with the new editor until the hidden field feature is available. Please add…would love to use these new forms!
Me too! I need the hidden fields 
We build attribution reports, clearbit data everything from these hidden fields.