Hey Brenden,
Thanks for your help on this topic (and all the other ones, too).
I maybe should have indicated this earlier, but the result I'm going for is the ability for an advanced content editor to populate these form fields with Macros, specifically concatenating a hyperlink with a macro - such as "http://someadvertisingsite/useremail={%CurrentUser.Email|(identity)GlobalAdministrator%}"
It doesn't sound like this is going to be possible in the Form tab context from what you're saying.
I wish that there was documentation that indicated where Macros are usable and where they are not in Kentico.