I don't believe there is a direct way to do it. I was hoping that by embedding \!n, the standard new line sequence that it would break the line, but it does not recognize it
You could draw the reference line without any label, and then use the << Add Graphics Script to add the info
names default to here(1);
dt = open("$SAMPLE_DATA/big class.jmp");
ow = Oneway(
Y( :height ),
X( :sex ),
SendToReport(
Dispatch( {}, "1", ScaleBox, {Add Ref Line( 65, "Solid", "Black", "", 1 )} )
)
);
report(ow)[framebox(1)] << add graphics script(
Text( Center Justified, {2, 65}, "Two" );
Text( Center Justified, {2, 64}, "Lines" );
);
Jim