Show ctrl-click function of shared orders button in tooltip

src/lang/extra/english.txt

@@ -1584,6 +1584,7 @@ STR_ORDERS_OCCUPANCY_LIST_TOOLTIP                               :{BLACK}Order oc
 STR_ORDERS_OCCUPANCY_PERCENT                                    :{NUM}%
 
 STR_ORDERS_NEW_GROUP_TOOLTIP                                    :{BLACK}Create group from single vehicle
+STR_ORDERS_VEH_WITH_SHARED_ORDERS_LIST_TOOLTIP_EXTRA            :{STRING}{}{BLACK}Ctrl+Click to create group from single vehicle
 
 STR_ORDER_GO_TO_WAYPOINT_REVERSE                                :Go via and reverse at {WAYPOINT}
 STR_ORDER_GO_NON_STOP_TO_WAYPOINT_REVERSE                       :Go non-stop via and reverse at {WAYPOINT}

src/order_gui.cpp

@@ -3517,6 +3517,22 @@ public:
 		}
 	}
 
+	bool OnTooltip(Point pt, int widget, TooltipCloseCondition close_cond) override
+	{
+		switch (widget) {
+			case WID_O_SHARED_ORDER_LIST: {
+				if (this->vehicle->owner == _local_company) {
+					uint64 args[] = { STR_ORDERS_VEH_WITH_SHARED_ORDERS_LIST_TOOLTIP };
+					GuiShowTooltips(this, STR_ORDERS_VEH_WITH_SHARED_ORDERS_LIST_TOOLTIP_EXTRA, lengthof(args), args, close_cond);
+					return true;
+				}
+				return false;
+			}
+			default:
+				return false;
+		}
+	}
+
 	const Vehicle *GetVehicle()
 	{
 		return this->vehicle;

src/timetable_gui.cpp

@@ -641,6 +641,14 @@ struct TimetableWindow : GeneralVehicleWindow {
 				GuiShowTooltips(this, STR_TIMETABLE_CLEAR_SPEED_TOOLTIP, 0, nullptr, close_cond);
 				return true;
 			}
+			case WID_VT_SHARED_ORDER_LIST: {
+				if (this->vehicle->owner == _local_company) {
+					uint64 args[] = { STR_ORDERS_VEH_WITH_SHARED_ORDERS_LIST_TOOLTIP };
+					GuiShowTooltips(this, STR_ORDERS_VEH_WITH_SHARED_ORDERS_LIST_TOOLTIP_EXTRA, lengthof(args), args, close_cond);
+					return true;
+				}
+				return false;
+			}
 			default:
 				return false;
 		}