I've been using the back-tick ("`" left of the number 1 ) as my shortcut for the Guake drop down terminal. I've set it for Guake from Guake's preferences.
Now, I've installed another terminal, Tilix. I want to make the back-tick the drop down shortcut for it. I could not find find this option from Tilix preferenes. So I went to "System Settings" -> "Keyboard" -> "Shortcuts".
Turns out that trying to associate the back-tick character with any command, does not work and instead it's Disabled