It should appear when you click on the blue label of the form outline and go to the properties inspector. If you attach a copy of the page you are working on I can test to see if it is a problem with the page itself.
What is it that you are trying to change? The reality is that Form Builder is a much better "builder" than it is an "editor" and when you re-enter the wizard to edit it will essentially delete the existing form and rebuild it. Often times edits should be done by changing the html, css, or server behaviors in Dreamweaver rather than rebuilding the form.