remove subplot titlesI want to get rid of subplot titles to get more space for the plots.
Hm, GraphBuilderGroupBoxes - quite uncooperative, as mentioned before 
https://community.jmp.com/t5/Discussions/Identifying-Titles-of-Graph-Builder-Page-Titles/m-p/426380/highlight/true#M67622
https://community.jmp.com/t5/Discussions/GraphBuilderGroupBox-lt-lt-Get-Window-Title-issue/m-p/423554
Seems that just the collapse and delete commands trigger some action, but even they don't help with the space consumption.
dt = Open( "$SAMPLE_DATA/Airline Delays.jmp" );
dt << minimize window( 1 );
gb = Graph Builder(
Size( 916, 659 ),
Show Control Panel( 0 ),
Graph Spacing( 5 ),
Variables( X( :Day of Month ), Y( :Month ), Group Y( :Distance ), Wrap( :Airline ), Color( :Arrival Delay ) ),
Elements( Heatmap( X, Y, Legend( 5 ) ) )
);
gbb = Report( gb )[Graph Builder Box( 1 )];
Boxes = gbb << xpath( "//GraphBuilderGroupBox" );
New Window( "wait ...", <<MODAL></MODAL>
Mass CustomizationRe: remove subplot titlesFrom @XanGregg 's Discovery Summit Talk
https://community.jmp.com/t5/Discovery-Summit-2014/Unlocking-the-Power-of-Graph-Builder/ta-p/22134
I learned that one can resize the subplot tiltes by dragging (~ 24min) - but the minimum size is still quite big.
Fortunately, via JSL one can do even better. The magic is done by the option
Size( xx )
of the Wrap command.
By dragging with the mouse, one can decrease it to 10, in JSL one can set it to 1 
dt = Open( "$SAMPLE_DATA/Airline Delays.jmp" );
dt << minimize window( 1 );
gb = Graph Builder(
Show Control Panel( 0 ),
Graph Spacing( 5 ),
Variables(
X( :Day of Month ),
Y( :Month ),
Group Y( :Distance ),
Wrap( :Airline, Size( 1 ) ),
Color( :Arrival Delay )
),
Elements( Heatmap( X, Y, Legend( 5 ) ) )
)
Re: remove subplot titlesI also noticed the "wrap" boxes - same size as a single-line standard box.
So, it helps a bit if the titles are really long and span over multiple lines.
Hm, tearing apart the plot and manually combining all boxes except the subplot titles could be an option ...
Perhaps as a universal button on the toolbar 
On the other hand, I really love to optimize a plot, click on "Save Script/To Database" and be sure that I can recreate the plot as it was.
Surprising that hide and collapse don't do what they could do ...
I opened a post with the wish to delete "wrap" subplot titles:
https://community.jmp.com/t5/JMP-Wish-List/function-to-delete-subplot-titles-orany-GraphBuilderGroupBox-in/idi-p/554858
a related wish: Function to adjusting the size of the titles:
https://community.jmp.com/t5/JMP-Wish-List/Right-click-to-change-Group-font-and-font-size/idi-p/116638

Re: remove subplot titlesThere does not seem to be a way to delete the subgroup area. Even deleting it, forces a group to be displayed with the title, "Wrap".
The only way that I can see that you could do what you want, is to create a new window, and copy just the frame boxes and the axis boxes from the original graph, to the new window.
Re: remove subplot titleslinked topic:
https://community.jmp.com/t5/Discussions/Reduce-font-size-for-wrapped-graph-builder-headings/m-p/6797#U6797
https://community.jmp.com/t5/JMP-Wish-List/Right-click-to-change-Group-font-and-font-size/idi-p/116638#U116638