Keyboard Shortcuts: Null and Spacebar are visibly identical

Hi,

In the Keyboard Shortcut editing dialog a null setting and the setting of the Spacebar are visually identical (blank). 

I suggest use of:

<Spacebar>    Alt-<Spacebar>  etc.

or similar.

Also, question:   How can we set a function explicitly to Null if the default (result of Reset) in non-Null?

IMO, we should always be able to null-out a Keyboard Shortcut setting.

Thanks.