New List Item Prompt Page
In the Advanced Options window, the New List Item Prompt page displays Prompt for additions to lists. This checkbox indicates whether the Add List Item window opens when a new list item is encountered in the source file for the import.
When it is selected (default), the Add List Item window opens so that you can can supply the code, display text, and value for the item.
When it is cleared, the Import Wizard assigns codes and descriptions to all new list items encountered during the import.