I know in X3 Producer there's a feature that is not on by default, called Auto Track Zoom, which is quite cool.  Turn it on under View > Auto Track Zoom within the Track view.   Shortcut is <Shift +  Z>.  Now, when you select any track and adjust its height all the other tracks will adjust to the same height at the same time. It's not the same thing as a key binding for minimize and maximize, but it might actually be better that what you were looking for.