Hi Jane

jane.e.fielding said:
Is it possible to sort on a field in the report writer but not display it?

Not that I am aware.

What I would recommend doing is create an additional number field, call it line, and add this code to a button or trigger

let a := 1;
for b in ChildTable order by CompoundSortField do
    b.(Line := a);
    a := a + 1
end

Now include the line field as the first column of your report, and use this as the sort order.  I see this commonly on documents and it looks highly professional.

Regards John