I'm aware of the various prefill options for cookied website visitor, but specifically asking about url parameters. With most form tools, I can easily grab the form Id by inspecting the page, then use a url parameter to set a value in that field when the pages loads.
Something like: mywebsite.com/contact?msdyncrm_code-12345=google-ad > passes the value /google-ad/ into a hidden msdyncrm_code field, which then writes to the database. It doesn't appear to work, even with a non-hidden field. It just isn't populating.
Am I missing something or is this functionality not supported in marketing forms? Or maybe Outbound but not Real Time?