You have support for 'zo' and 'zc' for opening and closing folds, but you lack support for 'za' which _toggles_ the fold.
Can that easy feature be added? :)
> Can that easy feature be added?
Not sure, but probably. I'd be happy to assist you if you'd like to add it.
Duplicate of http://sourceforge.net/p/jvi/feature-requests/54/