Have you actually used the program? Right now looking at sf2 would show two condensed labels..... punch and kick, whith the sub labels below it. Doing it the other way around makes no sense as only two of the three buttons share the same sub-label.
It is possible now that I understand what you mean, but it's a backwards way of thinking. You make three merged labels and link them to the two buttons each column rather than the row. The only problem is, in order for it to work, you have to delete the merged labels that are linked to the three buttons on each row. As 99% of all games have horizontal groupings, it doesn't make sense to do so. You can also make a merged label and merges two or more different merged labels, but again, this is far too confusing to be useable.