Due do the defining keyboard shortcuts on live (running) program in case of selecting active key there is a conflict:
* should program execute this keyboard shortcut
* or should it define it as keyboard shortcut

For example for "Compose an email message" and keyboard shortcut "N" the first option wins -- meaning it is impossible to bind such shortcut to this menu.

To reproduce.
* turn Claws into customizable keyboard mode
* select "Message" menu
* move mouse over "Compose an email message"
* press N
* get back to "Message menu"
* the shortcut was not changed -- BUG

(from my experience -- defining keyboard shortcuts should be done in separate window, when you can interpret all the input by yourself).