Given the structure of how you are approaching your analysis, I would handle the deletion of the text box, by deleting it before appending the output to your V List Box.
Names Default To Here( 1 );
// Open Data Table: big class.jmp
// → Data Table( "big class" )
Open( "$SAMPLE_DATA/big class.jmp" );
ncol = N Col( Data Table( "big class" ) );
combo = V List Box();
w = New Window( "Run Charts",
H List Box( combo )
);
For( i = 4, i <= ncol, i++,
plot = V List Box(
cc = Control Chart Builder(
Test Excluded Subgroups( 1 ),
Variables( Y( Column( i ) ) ),
Where( :sex == "F" )
);
);
(report(cc)<<parent)[textbox(1)]<<delete;
combo << append( plot );
);
The report element for a platform points to the first Outline Box() in the report, not to the HeadBox() as the Current Report() function does. Therefore, one needs to move to the parent above the first OutlineBox() and the find the first text box() from that point.
Jim