Mutter supports the 'Above_Tab' fake keysym that refers to the key that is physically located above the tab key. It is used in the default shortcut of the "Switch windows of an application" action.
As gtk_accelerator_parse() doesn't recognize the keysym, we display the shortcut incorrectly as "disabled", and it is not taken into account for conflict resolution.
Address this by translating binding that contains the 'Above_Tab' string to bindings where the string is replaced with each possible keysym that corresponds to the fixed keycode of KEY_GRAVE + 8.
Fixes #581 (closed)