I would think how to make this a bit more robust, but you can change the Horizontal of the list box which contains those OutlineBoxes to 0
Names Default To Here(1);
dt = Open("$SAMPLE_DATA/Big Class.jmp");
dist = dt << Distribution(
Continuous Distribution(
Column(:height),
Horizontal Layout(1),
Vertical(0),
Normal Quantile Plot(1),
PpK Capability Labeling(0)
)
);
lb = ((Report(dist)["Quantiles"] << parent) << parent) << Set Horizontal(0);
Edit:
If you have to do this only once and you don't want to script, you can also do this interactively using display tree's properties (this doesn't seem to be captured in the script created by JMP)
-Jarmo