If the document you are editing contains variables not yet in the variables list displayed in the Create Variables Assistant, you can add those variables to the list. Simply click the 'Add New Variables to List' button (1).
If you want to add instructions or provide examples for other users to follow as they complete the IDB form, click the Show IDB button (2). This will bring up the classic Instant Database screen where you can edit the variables to your heart's content. See Making Input Form Entries More Meaningful and Organizing Input Form Entries