You can get the results by having a 2 level x axis and Overlaying by treatment
Graph Builder(
Size( 531, 464 ),
Show Control Panel( 0 ),
Variables(
X( :experiment ),
X( :treatment, Position( 1 ) ),
Y( :value ),
Overlay( :treatment )
),
Elements( Bar( X( 1 ), X( 2 ), Y, Legend( 13 ) ) )
);
Jim