How to re-assign Tab key in "Keyboard Shortcuts"

I want my Tab key to do something different instead of toggling Composition Mini-Chart. But when I try to assign it to something else in "Keyboard Shortcuts", I can't do it, because when I try to and press "Tab", it is intercepted by After Effects GUI and it selects the next GUI control inside the "Keyboard Shortcuts" dialog, instead of assigning it to the selected command. So, how can I re-assign the Tan button then?

This seems to be problem to me, since theoretically it should be possible, but in practice it doesn't work.