At any time, you can modify fields in an Object Definition File that is loaded in the Designer.
In the Statement Designer—Object Definition Editor window, click the plus sign icon preceding the Object containing the field you want to modify. Then click the plus sign icon preceding Fields.
Highlight the field name you want to modify in the object tree.
Either right-click and select Modify... or click the Modify icon.
Make changes to the fields on the Modify field dialog box.
Click OK to save the change(s) or Cancel to discard the change(s) and return to the object tree.