Adding New Items on Factory Toolbars

Please notice the following screenshot and you will understand how to add a new item to any of the toolbars.

Once you add a toolbar button, most probably you would be thinking about inserting custom HTML to the editor. A typical use can be adding a button labeled "Insert Signature" for inserting your custom signature HTML.

So, here is the snippet that can be useful for you.

        private void btnInsertSignature_Click(object sender, EventArgs e)
        {
            winFormHtmlEditor1.Content.InsertHtml(
                "<p>James Paul <br/><span style=\"color:blue;\">Executive Officer</span>"
                + "<br />james_paul@some_domain.com</p>", false);
        }