For the next PR, I've added this possibility.
At the moment if you go to a Sort tab for a browse field, there's an option there
"Default to Descending Sort Order".
At the moment that only works if the field is set as the default sort order, but for the next PR I've changed it so you can set it for all columns.
I'm hoping to have the PR out tomorrow - I'm just finishing some changes I've been wanting to make for a while.
cheers
Bruce