Well, you didn't specify how you wanted to organize them. You're right, I
don't see a way to reorder the groups themselves. They appear to be in
chronological order by when they were created. That being the case, you
could create a temporary group, move the icons from one group into that one
then delete the now empty group and recreate it then move the icons back. Do
this in the order you want the groups to appear. I know it's not pretty, but
it should work. When you're done, delete the temporary group.