Total Commander

I'm talking about Misc. configuration dialog: in its Comman: field (where command is displayed) Backspace does nothing but it may change command to 'no remap'. This will allow faster unbinding keys: just select combination, press backspace in command editbox (it is read-only anyway) and then press green mark button.

Ah, sorry, I thought that you meant the dialog where you choose the internal commands (which appears after clicking on the magnifying glass).