Hi Holly,
The best way to do this is to simply double-click on the Splitter.
Simply navigate to the Splitter then use VO keys+shift+space+space
which will perform the double-click that a sighted person may
normally use. When you perform this action, it toggles the Pane on
and off. some folks have had problems with this but it has always
worked for me. I have my cursor tracking settings all checked in VO
Preferences. You can do it without these settings but you'll have to
make sure that the mouse is at the splitter when you perform the
double-click.
HTH.
Later...
Tim Kilburn
& Carter the Canine
Fort McMurray, AB Canada