how to bind C-M-Backspace somewhere else?

[Paul Pogonyshev]

Sorry for a bit off-topic question, but I thought Emacs users are the
ones who might have encountered the same problem.

How do I rebind X's restaring key combo (C-M-Backspace) somewhere else,
preferably to C-S-M-Backspace?  I ask because I accidentally hit it
for several times now, mistook for Emacs C-M-\ (`indent-region'.)  On
my keyboard `\' and `Backspace' keys are next to each other.

Paul