KMail View

I'm getting used to Kmail in the KDE4 version. 

When I started adding all my old email and rebuilding filters, etc, In the 
second window with all the folders in it, there were two sections - one at the 
top where I could move my most important folders, and one below it for 
everything else.

I don't know how I've done it but the top part of the window has disappeared 
and I don't know how to bring it back. 

It certainly makes it much more useful.

Anyone know what it's called, and where I find controls for it's appearance?

Bob