Dual Vertical mistake

Hi all:

I have turned something on which I can not figure out how to turn it off. When I go to a dual vertical lister it opens up in two tabs vs a split window. How do I fix this so it's the split view?

You must have saved over the Dual Vertical style.

Just set the lister up how you want it, right-click the Dual Vertical tab and select Update to save over it again.