...
Adding plugins isn't well documented but I have created a Comment plugin that works like sticky notes. Insert to demonstrate the process of creating plugins. You can insert a note and comment and it will appear when the mouse passes over the stick pinstickpin. It is still a work in progress (editing of existing comments has not been implemented and deleting one is a bit problematic.) but it will demonstrate the process.
To install, unzip the attached comment.zip file and put in the fckeditor/editor/plugins directory. Put the following line in your myconfig.js file after FcKConfig.PluginsPath:
...