This applies to the Copy To {Left|Right} Pane buttons and the Copy From {Left|Right} Pane buttons (sorry, I got the names slightly wrong) and the Shift-Pane-{Left|Right} menu items should be visibly disabled (grayed out) when thee corresponding operation is logically impossible as a result of the source/destination pane being "to the left of Pane 1" or "to the right of Pane N" where N is the number of panes. This is a cosmetic chnage, but it would make it a little easier to get comfortable with the very flexible/powerful interface and pick the intended operation more quickly.
I would specifically not want the panes to be treated cyclically, i.e., the pane to the "left" of Pane 1 is Pane N, and the pane to the "right" of Pane N is Pane 1. That would just be asking for trouble I think.
Kyle