[ JDK VERSION : 1.6.0_07 ]

Suppose, I have one pane at the bottom of editors pane and right of
the Navigator's pane, contenting 7 tabs.
If I want to give this the whole width, so it would be below
Navigator AND Editor, I have to move all those 7 tabs solely. That'
annoying.

My suggestion: make separators between the panes dragable/movable to
squeeze affected neighbour pane.

The end of the story: Starting the debugger, it had opened a 5th
pane, between editor and bottom pane, but right of Navigator.
Editor's pane was really small after. So I had to move all debugger
tabs separately to bottom.
... and always, if I open a new thing from menu->Windows, it opens in
this stupid 5th pane.