Comment 5 for bug 1232894

Oliver Sauder (sao) wrote :

Decision has been made to drop the internal Diodon hotkey feature and leave the responsibility of register a custom shortcut up to the desktop environment.

You can find more details here how you can do this:
https://esite.ch/2015/07/using-custom-shortcuts-of-de-as-diodon-hotkey/

Depending on the DE you use but symbols in keybindings should work otherwise will it be an issue of the specific desktop environment.