EditorWindow.position  

var position : Rect

Description

The position of the window in screen space.

Setting this value will undock the window if it's docked

Create an empty editor window of 200x200px.

// Create an empty editor window of 200x200 pixels size
// located at the top left corner  

class EditorWindowPosition extends EditorWindow {
    @MenuItem ("Example/Window position usage")
    static function Init () {
        var window = EditorWindow.GetWindow(EditorWindowPosition);
    window.position = Rect(0,0, 200,200);
    }
}