This window is only accessible if you set up Lookup type UDFs in Module Preferences.

If you want to track or categorize specific information, you can create code-type User-Defined Fields and then create User-Defined Codes to enter in those fields.

User-Defined Fields are created on the User-Defined Fields tab in Module Preferences. After you set up a code-type User-Defined Field in Module Preferences, you can set up Codes to enter in those fields by selecting Options > Set Up User Defined Codes from the navigation pane.