During the process of creating a form definition, you may change your mind about a field you defined. To delete a field definition:
On the image of the form, select the field you want to delete.
Press F9 on your keyboard.
To delete fields that are not yet defined but only drawn or double-clicked, press F9 or use Delete latest selection.
If a field definition cannot be deleted, it may be because the form definition is Active. See Editing an active form definition.