Why do some menu commands not work when bound to global keyboard shortcuts?
Context menu commands require a list of tracks on which to operate. If you execute them from the context menu or using a normal (non-global) keyboard shortcut, this list is provided by part of the program where you used the context menu or the keyboard shortcut (the context). For global keyboard shortcuts there is no way to chose a list of tracks automatically when they are used, so you have to chose a context when you bind the command. To do so, select a command from the [context / now playing] or [context / playlist] branch to make the command use the playing track or the selected items on the active playlist when you press the global keyboard shortcut.