You could use the color dropzone to specify the symbols for the additional layer in the data:

dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
New Column( "Row",
Formula( Row() )
);
Graph Builder(
Size( 501, 291 ),
Show Control Panel( 0 ),
Variables( X( :Row ), Y( :height ), Y( :weight, Position( 1 ) ), Color( :sex ) ),
Elements(
Line(
X,
Y( 1 ),
Y( 2 ),
Color( 0 ),
Legend( 17 ),
Summary Statistic( "Mean" )
),
Points( X, Y( 2 ) ),
Points( X, Y( 1 ) )
)
);