You can search for the localized value only in limited scenarios.
The screens that support the indexed searches automatically enable the search by localized value, as the index includes the localized value.
The DisplayLocalizedFieldInLocale input variable normally controls the output behavior. In some cases and depending on the API behavior, you can also search for the localized value. For more information about the API behavior, see the Sterling Selling and Fulfillment Foundation: Javadocs.