One option is to use some scripting and add graphic script
Names Default To Here(1);
dt = Open("$SAMPLE_DATA/Big Class.jmp");
gb = dt << Graph Builder(
Variables(X(:weight), Y(:height)),
Elements(Points(X, Y, Legend(3))),
SendToReport(
Dispatch(
{},
"height",
ScaleBox,
{Add Ref Line(65, "Solid", "Black", "", 1),
Add Ref Line(55, "Solid", "Black", "", 1)}
)
)
);
rep = gb << report;
framebox = rep[frame box(1)];
framebox << Add Graphics Script(
Transparency(0.5);
Fill Color("Gray");
Rect(X Origin(), 65, X Origin() + X Range(), 55, 1)
);
-Jarmo