I'm not sure if I understand your problem,
I have no problem in displaying large texts in a heatmap, see example.
And if I even need more text in a box, I press CRTL+SHIFT+"-" to reduce font size, and everything fits.
BR
Names Default To Here( 1 );
dt = Open( "$SAMPLE_DATA\Aircraft Incidents.jmp" );
Graph Builder(
Size( 495, 489 ),
Show Control Panel( 0 ),
Graph Spacing( 5 ),
Variables( X( :Final Narrative ) ),
Elements( Treemap( X, Legend( 2 ) ) ),
Local Data Filter(
Conditional,
Add Filter(
columns( :Accident Number ),
Where(
:Accident Number == {"ANC01FA033", "ANC01FA084", "ANC01FA093", "ANC01FA095", "ANC01FA100",
"ANC01FA102"}
),
Display( :Accident Number, N Items( 15 ), Find( Set Text( "" ) ) )
)
)
);
Georg