When entering keyboard shortcuts for a button, I first tried clicking on the whole field with "None" written on it, instead of the "x" on the right. Canceling "nothing" and only then being able to set the keyboard shortcut seems a lil bit counterintuitive.
For changing already set shortcuts, I also felt rather directly clicking on the field, than clicking on the "x". But maybe it is more error proof this way, so I get it if its meant to work like this, but I wanted to share my feeling about it.