Try the example script below, although I am not sure if the result is anywhere near what you want. The trick seem to be to add all the columns twice and exclude the target variable from the bar chart and the other two variables from the "target chart", here represented by a box plot. Variable exclusion (X or Y) are found in the contextual menu (right click).
dt = Open( "$ENGLISH_SAMPLE_DATA/Big Class.jmp" );
dt << New Column( "target", Numeric, Continuous, <<Set Each Value( 100 ) );
Graph Builder(
Size( 500, 300 ),
Variables(
X( :height ),
X( :target, Position( 1 ) ),
X( :weight, Position( 1 ) ),
Group Y( :age )
),
Elements(
Bar( X( 1 ), X( 3 ), Legend( 2 ), Bar Style( "Bullet" ), Summary Statistic( "Mean" ) ),
Box Plot( X( 2 ), Legend( 4 ), Box Style( "Solid" ) )
),
SendToReport(
Dispatch( {},"400",
ScaleBox,
{Legend Model( 2, Properties( 1, {Transparency( 0.5 )} ) ),
Legend Model( 4, Properties( 0, {Fill Color( 0 )} ) )}
)));
