EditorApplication.ExecuteMenuItem  

static function ExecuteMenuItem (menuItemPath : String) : boolean

Description

Invokes the menu item in the specified path.

This function also works with Editor Scripts

// Simple script that lets you create a new
// scene, create a cube and an empty game object in the scene
// Save the scene and close the editor

import UnityEditor;

@MenuItem ("Example/Chain Actions and close")
static function Chain() {
    EditorApplication.NewScene();
    
    EditorApplication.ExecuteMenuItem("GameObject/Create Other/Cube");
    EditorApplication.ExecuteMenuItem("GameObject/Create Empty");

    EditorApplication.SaveScene("Assets/MyNewScene.unity");
    EditorApplication.Exit(0);
}