In 2.6 there was a shorcut key, Ctrl + Tab, that moved focus between
the docked windows and the editor. In that way you could always get to
the open windows from the editor, even if the windows did not have any
Now it is only possible with the windows that have defined a mnemonic,
which is always a number.
But even in the case of the window messages (mnemonic 0), it is easier
to press Ctrl + Tab than Alt + 0.