Add a fourth radio option. If selected we can use an expression to set the sort order based on other column(s) in the same table.
e.g. my table has categoryName, categorySequence
I would select the new option, and sort expression would simply be [categorySequence]
I've come across the need for this in about 80% of spotfire projects.
Even an option to "use the order the data is already sorted in" would suffice. The major annoyance is spotfire ignores data sorts here.