The default extension hotkeys can't be changed right now. One way to work around this for Windows users is to download and install the AutoHotkey program. Create a file named Firefox.ahk and then copy the code at the bottom and paste it into the file. Place this file in the Startup folder and then run it. Now, if a user presses Win-G in a Firefox window, it will invoke this extensions Alt-Z pause hotkey. The Win-G hotkey can be changed in the file to whatever hotkey is desired ( https://autohotkey.com/docs/Hotkeys.htm ).

$#g::
ifWinActive, ahk_exe firefox.exe
{
send !z ; Alt-Z extension pause hotkey
return
} else {
send #g ; Win-G hotkey
return
}