diff --git a/src/widgets/build_vehicle_widget.h b/src/widgets/build_vehicle_widget.h
--- a/src/widgets/build_vehicle_widget.h
+++ b/src/widgets/build_vehicle_widget.h
@@ -18,10 +18,12 @@ enum BuildVehicleWidgets {
 	WID_BV_SORT_ASSENDING_DESCENDING, ///< Sort direction.
 	WID_BV_SORT_DROPDOWN,             ///< Criteria of sorting dropdown.
 	WID_BV_CARGO_FILTER_DROPDOWN,     ///< Cargo filter dropdown.
+	WID_BV_SHOW_HIDDEN_ENGINES,       ///< Toggle whether to display the hidden vehicles.
 	WID_BV_LIST,                      ///< List of vehicles.
 	WID_BV_SCROLLBAR,                 ///< Scrollbar of list.
 	WID_BV_PANEL,                     ///< Button panel.
 	WID_BV_BUILD,                     ///< Build panel.
+	WID_BV_SHOW_HIDE,                 ///< Button to hide or show the selected engine.
 	WID_BV_BUILD_SEL,                 ///< Build button.
 	WID_BV_RENAME,                    ///< Rename button.
 };