How to add a keyboard shortcut to Firefox Quantum using the CTRL key

Question

How do I add an keyboard shortcut to Firefox 57+ (Quantum) using the CTRL-Key? I use Windows 7, and wish to alter the key bindings to add a function not found at Mozilla's list. I tried the add ons Saka Key, Shortkeys, and Vinium-FF but they don't allow use of the CTRL key; I also searched for any method involving edits to the config files, to no avail.

I want to use, for example CTRL-X to change to offline mode, which now must be performed with {MENU} | More | Work Offine . With Quantum there's no way to do those steps except by mousing. There might be other things to add in the future, but that's the immediate objective.

Is there an option I didn't notice or is it just not possible? Some posts say shortcuts aren't possible at all but I'm not sure because I found the add ons doing just that.

Answer 1

Alt-F K or Alt F K
will do the job with no changes, extensions, or edits.

Tried to create a Ctrl- based hotkey with AutoHotKey, a free, open-source scripting language for Windows. So far, the script isn't working as it should; it stalls after getting to the Files menu. I've tried

   ^x::   
   Send !fx  
   Return  

and

   ^x::  
   Send !f  
   Send, {Up 2}  
   Send, {Esc}  
   Return  

However, since Ctrl-X is a standard for cutting text or data which predates Microsoft Office, going back to when IBM's Common User Access and PC-DOS were Hot Stuff, finding a different keystroke combination not in common use is Highly Recommended. I know Ctrl-X is hotwired into my limbic system, and thinking about using it for something else give me the Willies.