A first question would be why you want to disable the shortcut, but I assume there will be a reason, such as because you want to use it for some other application. If so, you could consider changing that application’s shortcut, but of course we respect your choice. Second, if the confirmation dialog "apparently doesn’t work", chances are you have set Firefox to behave in a way your tabs wil be restored anyway at startup which can or will overrule the dialog, given the number of support questions ending with that conclusion. More info about these conditions and how to restore them can be found in [[Startup, home page, tabs, and download settings|this support article]]. If that does not help, it may also be good to name the add-on that does no longer work or have a look at one using the [https://mozilla.github.io/extension-finder/ Extension finder] page in order to find a replacement for it. Last, if nothing helps, you could consider editing the file(s) containing the strings and shortcuts for Firefox and repacking them, so you would be able to change the q to another key. Please let us know if you need help for that.