Search in Equipment Hierarchy Extension Control

When adding a new notification via the NotificationCreateUpdate.page, the Search field in the Equipment Hierarchy List Picker, seems to expose only the equipment ID {EquidId} and description {EquipDesc} fields. Searching by any other field does not work, even if it is displayed in the footnote area. How might one expose other fields (e.g. inventory number {InventoryNum) to the search? The BusinessObjects Target setting for QueryOptions (EquipmentQueryOptions.js) does not incorporate explicit filter(s) using a context.searchString as can be done with an oData target for a regular (non-extension) control.