You can make a choice list modifiable by checking User Modifiable under the Lists menu. First, click List Editor in the Tools menu to open the List Editor dialog. Then, select the list that you want to be modifiable from the List of Lists table. Next, select User Modifiable from the List menu. A checkmark is placed in the List menu to show that the chosen list is modifiable.
When a choice list is modifiable, a user can alter the list of items that is displayed as a choice list. To make it so it is not modifiable, you simply uncheck the User Modifiable option from the List menu.
Note: The Enable/Editable option in the List Editor dialog is only used for lists displayed in hierarchical lists or tab control. It applies to each element of the list.