After startup world editor, i can't control the vehicles or go to the menu. Nothing can be started and all icons will disappear and only the world editor can be used again.
Press Alt U. It can bring back the ui apps if closing world editor couldn't do it. And if you can't control your vehicle after/when using world editor, enable drive in editor in the toolbar of world editor in top left of the screen. There's a picture of a car on that button.