AddParent

using UnityEngine;

using UnityEditor;

using System.Collections;

public class AddParent : ScriptableObject

{

    [MenuItem ("GameObject/+Add Parent")]

    static void MenuInsertParent()

    {

        Transform[] transforms = Selection.GetTransforms(SelectionMode.TopLevel |

            SelectionMode.OnlyUserModifiable);
GameObject newParent = new GameObject("_Parent");

        Transform newParentTransform = newParent.transform;
if(transforms.Length == 1)

        {

            Transform originalParent = transforms[0].parent;

            transforms[0].parent = newParentTransform;

            if(originalParent)

                newParentTransform.parent = originalParent;

        }

        else

        {

            foreach(Transform transform in transforms)

                transform.parent = newParentTransform;

        }

    }

}

AddParent