Your placement of the Spacer Box and the size of the Spacer Box is all that needed to be changed to get your code to work
Names Default To Here( 1 );
Open( "$SAMPLE_DATA/Big Class.jmp" );
New Window( "Spacing",
Lineup Box( N Col( 2 ), Spacing( 0 ),
Variability Chart( Y( :height ), X( :age, :sex ), Std Dev Chart( 0 ) ),
V List Box(
Distribution(
Continuous Distribution(
Column( :height ),
Quantiles( 0 ),
Summary Statistics( 0 ),
Horizontal Layout( 1 ),
Vertical( 0 ),
Outlier Box Plot( 0 )
)
),
Spacer Box( size( 1, 150 ) )
)
)
);
Jim