I am learning on the fly. JMP 14 already has a feature that fulfilled my wish list: the CaptionBox has a factor checkbox so it work for each category displayed on the X-Axis.
This displays the 5 number summary (min, Q1, Median, Q3, max) and the means as a caption box.
 
 Here is the script showing the customization, for just the first boxplot.
Here is the script showing the customization, for just the first boxplot.
Graph Builder(
	Size( 1029, 608 ),
	Show Control Panel( 0 ),
	Variables( X( :Month ), Y( :Sales ) ),
	Elements(
		Box Plot( X, Y, Legend( 6 ), Name( "5 Number Summary" )(1) ),
		Line( X, Y, Legend( 7 ) ),
		Caption Box(
			X,
			Y,
			Legend( 9 ),
			X Position( "Middle" ),
			Y Position( "Bottom" ),
			Per Factor( 1 )
		)
	),
	SendToReport(
		Dispatch(
			{},
			"Sales",
			ScaleBox,
			{Min( 50 ), Max( 700 ), Inc( 100 ), Minor Ticks( 1 )}
		),
		Dispatch(
			{},
			"Graph Builder",
			FrameBox,
			{DispatchSeg(
				Box Plot Seg( "Box Plot (June)" ),
				{Box Style( "Solid" ), Confidence Diamond( 1 ), Fences( 0 ),
				Fill Color( {162, 43, 221} )}
.....