You need to Programmatically populate the Code Snippet dropdown.

 

if (!IsPostBack) {
   CuteEditor.ToolControl toolctrl=Editor1.ToolControls["Codes"];
   if(toolctrl!=null) {
      CuteEditor.RichDropDownList dropdown=(CuteEditor.RichDropDownList)toolctrl.Control;
      //the first item is the caption
      CuteEditor.RichListItem richitem=dropdown.Items[0];
      //clear the items from configuration files
      dropdown.Items.Clear();
      //add the caption
       dropdown.Items.Add(richitem);
      //add text and value
      dropdown.Items.Add("Email signature","<h3>this is my email      signature</h3>");
      //add html and text and value
      dropdown.Items.Add("<img border=0 align='absMiddle' src='/data/contact.gif'/> Contact us","Contact us","support@cutesoft.net");
   }
}