We created new TinyMCE plugin following the recommendations from http://wiki.moxiecode.com/index.php/TinyMCE:Creating_Plugin. We put the new plugin folder in the Alfresco install alfresco/scripts/tiny_mce/plugins/ Then updated web-client-config-wcm.xml to add the button for the plugin. This is apparently not enough. What else do you need to do? How do the plugin get registered? There is a table folder for a table plugin in the plugins directory, if we remove that folder and rename our new plugin folder as 'table' then it picks up our plugin under that name.