I do have minor problems using subgroup in string grid.
I use the sample program asg38.dproj containing groups.
If I add column titles in the property ColumnHeaders as follows:
'Car'
'CarType'
'CC'
<etc>
It works fine - the title "Car" has disappeared as expected
But if I add a subgroup, the columns are displaced, meaning that the column titles no longer fits the cell contents.
I couldn't find a sample program containing subgroups.