From the help file: It is very easy to customize the layout of the toolbars in RichTextEditor. You can add or remove buttons, and change their placement. Beyond this, you may also add your own tools to the toolbar, create your own toolbars, or create custom icons for your toolbar! 

How  do I add my own tools and events  to the toolbar?

Hi rhonsberger,

Please refer to the examples below, it shows you how to add the custom button for the toolbar. You can find the full source code from the download package.

http://richtexteditor.com/demo/custom_buttons.aspx

http://richtexteditor.com/demo/custom_buttons2.aspx

http://richtexteditor.com/demo/custom_buttons3.aspx 

Regards,

Ken