public class NewBehaviourScript : MonoBehaviour
{
    private Rect uiWindow2 = new Rect(UnityEngine.Screen.width / 2 + 20, 20, 120, 400);
    private void OnGUI()
    {
        uiWindow2 = GUILayout.Window(34566, uiWindow2, DisplayUIWindowX, "TEST");
    }
    private void DisplayUIWindowX(int windowId)
    {
        GUILayout.BeginVertical(GUILayout.ExpandWidth(true), GUILayout.ExpandHeight(true));
        {
            //Header
            GUILayout.BeginVertical("box", GUILayout.ExpandWidth(true), GUILayout.ExpandHeight(false));
            {
                //Toolbar
                {
                    GUILayout.BeginHorizontal(GUILayout.ExpandHeight(false));
                    {
                        //Header
                        GUILayout.Label("TEST", GUILayout.ExpandWidth(true));

                        //Options
                        if (GUILayout.Button("O", GUILayout.ExpandWidth(false), GUILayout.ExpandHeight(true)))
                        {
                        }
                    }
                    GUILayout.EndHorizontal();

                    //Options
                }
            }
            GUILayout.EndVertical();

            //Content
            GUILayout.BeginVertical("box", GUILayout.ExpandWidth(true), GUILayout.ExpandHeight(true));
            {
                //Abstract
                //this.DisplayUIWindowBase();
                GUILayout.FlexibleSpace();
            }
            GUILayout.EndVertical();

            //Info
            GUILayout.BeginVertical("box", GUILayout.ExpandWidth(true), GUILayout.ExpandHeight(false));
            {
                GUILayout.BeginHorizontal();
                {
                    GUILayout.Label("Info: " + "", GUILayout.ExpandWidth(true));
                    if (GUILayout.Button("Clear", GUILayout.ExpandWidth(false), GUILayout.ExpandHeight(true)))
                    {
                        //info = "";
                    }
                }
                GUILayout.EndHorizontal();
            }
            GUILayout.EndVertical();
        }
        GUILayout.EndVertical();

        GUI.DragWindow();
    }
}