For some reason you cannot display reference lines on main Y-axis if you are using Normal Probability as axis type.
Names Default To Here(1);
dt = Open("$SAMPLE_DATA/Big Class.jmp");
ow = dt << Oneway(
Y(:weight),
X(:sex),
All Graphs(0),
Plot Quantile by Actual(1),
SendToReport(Dispatch({"Normal Quantile Plot"}, "2", ScaleBox, {Label Row({Show Major Grid(0), Show Major Labels(0)})}))
);
//calculate quantiles
//set reference lines
axisbox = Report(ow)[AxisBox(1)];
axisbox << Add Ref Line(0.05, "Solid", "Black", "5%", 1, 1, Label Settings({Label Position("Outside"), Opposite Axis(0)}));
axisbox << Add Ref Line(0.2, "Solid", "Black", "20%", 1, 1, Label Settings({Label Position("Outside"), Opposite Axis(1)}));
axisbox << Add Ref Line(0.5, "Solid", "Black", "50%", 1, 1, Label Settings({Label Position("Inside Inline"), Opposite Axis(0)}));
axisbox << Add Ref Line(0.1, "Solid", "Black", "10%", 1, 1, Label Settings({Label Position("Outside"), Opposite Axis(0)}));
wait(2);
axisbox << Scale("Linear");
axisbox << Show Major Labels(0);
axisbox << Show Major Grid(0);
wait(2);
axisbox << Scale("Normal Probability");
axisbox << Show Major Labels(0);
axisbox << Show Major Grid(0);
-Jarmo