WPF generates the value for ID attributes, so I had to use a call to IDGenerator.getCurrentID to get my hands on that value and store it. The value inline_widget is static and is what the builder uses internally, take a look at the source tab in the designer and you'll see what I mean. It is important to put this script immediately after the placeholder for the builder richTextEditorGoesHere or it won't work.
If we run our model we should now see a new icon on the toolbar which will cause the rich text editor to maximize when clicked:
I think that covers all the details, pretty cool stuff! I wish the guys at IBM would have put this in the builder, but we can still work around it.