Hidden fields

Hi all.

I am trying to utilise a hidden field in one of my forms and I don’t seem to be able to. Is what I’m doing impossible or am I doing it wrong?

I have put this field on my form: [hidden text text-848 placeholder “blah”]

When I reference the field in the mail message body, i.e. [text-848], the email produced simply includes the literal “[text-848]”.

If I remove the “hidden” modifier, the content of the field is inserted into the mail message correctly. What am I doing wrong and/or how can I use hidden fields?

Thanks in advance

David