Can anyone tell me how I can use the V11 DDF Builder to change a field size to use space at end of file rather than next column?

My Data files currently do not match the ddf's and I'd like to fix my ddf's.

Popup Hint in ddf builder table editor says press Shift key but I can't get it to work. It seems only to use space from next column and will only resize a column providing there is enough space in following column to steal from.

If Column A is 20 and Col B is 10 and last column is 100 I'd like to make col A 40 and thereby reduce last undefined column to 80.

Getting frustrated - need help!