FYI, you can do this kind of thing (so with the ability to change the order of the grid and reference lines you may be able to get what you want):
Names Default To Here( 1 );
Open( "$SAMPLE_DATA/Big Class.jmp" );
biv = Bivariate( Y( :weight ), X( :height ), FitLine );
rbiv = biv << report;
framebox = rbiv[frame box( 1 )];
Wait(1);
framebox <<
Add Graphics Script(
1,
Description("Orange Polygon"),
Transparency( 0.5 );
Fill Color( {1.0, 0.5, 0.0} );
Polygon( [60, 72, 57], [75, 120, 120] );
);
Wait(1);
framebox <<
Add Graphics Script(
2,
Description("Blue Polygon"),
Transparency( 0.5 );
Fill Color( {0.0, 0.5, 1.0} );
Polygon( [60, 72, 57], [150, 120, 120] );
);
Wait(1);
framebox << Remove Graphics Script( 1 );
// Having removed the first graphics script, the second is now in position 1 (even though it was assigned originally to position 2) . . .
Wait(1);
framebox << Remove Graphics Script( 1 );
Also, please see: https://www.jmp.com/support/help/Adding_Scripts_to_Graphs.shtml