What is Wrong With The Simplest Menu ?

Question

using System.Windows.Forms;

public class mymenu : MenuStrip
{
    public mymenu()
    {
        this.myitem = new ToolStripMenuItem();
        myitem.Text = "My Item";
        this.Items.Add(myitem);
    }

    private ToolStripMenuItem myitem;
}

... actually nothing wrong with it, you can drag it to your form
and hey it is working but this is not my question.
my question is :

after you drag it to a form, although you can add new items to it,
how can you make VS designer edit the current items
such as (myitem), change text, add event handlers ?
you can not do that , why ?

thanks

Silvia