Hi,

If the web site has settings to change the keyboard shortcuts used inside that site you would have to change the site options/settings and save it on the site. For the general Firefox keyboard shortcuts please see this.

Hello, thanks for your reply. I know the keyboard shortcuts of Firefox and I need to change one of them, because it prevents me. Ways to do this, I have not found the link you gave me. Google also does not help me. (translated by Google Translator)

Customizable Shortcuts can only change Firefox shortcuts. For shortcuts like Ctrl + \ that work in specific sites you would usually have to change it in the site's options/settings. If the issue is with Customizable Shortcuts, please see this.

The problem is similar to https://github.com/ttaubert/customizable-shortcuts/issues/10 But judging by the fact that it was created in November 2011, I probably want to know how to remove unnecessary to me key combination Firefox

Most probably the developer will reply to your query at AMO within a few days. The add-on is being actively developed, so most of the problems/bugs would probably be resolved by the next update. You can also try the add-ons forum where there could be users using the same add-on and may be able to provide workarounds. You can also try to access and change the Options via Tools (Alt + T) > Add-ons > Extensions.