I haven't found a shortcut and holding down cmd to broadcast the format command to all columnboxes seems not work, as you say.
The way I do it is to double-click on a numeric column to open the "Column Numeric Format dialogue, enter the desired format and then tab through the check boxes while hitting the return key for each target column (JMP12 for Mac).
It is also of course possible to do with JSL. An example:
dt = Open("$SAMPLE_DATA/Big Class.jmp");
ow = dt << Oneway(Y(:height), X(:age), Quantiles(1));
// Set nr of decimals for all Number Col Boxes in a Table Box
i = 1;
While(
Is Scriptable(Try(ncb = Report(ow)[Outline Box("Quantiles")][Number Col Box(i)])),
ncb << Set Format("Fixed Dec", 8, 1);
i++;
);
To apply it to any (current) report, the code below could be used (run in script window or as a custom menu item).
Names Default To Here(1);
// Get list of Table Box(Outline) titles
L = {};
i = 1;
While(Is String(Try(L[i] = (r[Table Box(i)] << parent) << get title)), i++);
// Dialog to choose Table Box and numeric format
New Window("Set numeric format",
<<modal,
cb = Combo Box(L),
Table Box(
String Col Box("", {"Width", "Dec"}),
nceb = Number Col Edit Box("", [8, 2])
),
Button Box("OK",
tb = cb << get selected;
{w, d} = nceb << get;
)
);
// Apply format to all num columns of Table
r = Current Report();
i = 1;
While(Is Scriptable(Try(ncb = r[Outline Box(tb)][Number Col Box(i)])),
ncb << Set Format("Fixed Dec", w, d);
i++;
);