Addition of a 'toggle' button to items' toolbar

Hello,
thank you for releasing your great code in the open.
I'm from the Italian National Research Council (www.cnr.it), we're looking into Your plugin to edit some metadata models in Alfresco. 
We've added a small feature which enables to collapse xml elements in the visual editor, as to save screen-space, and focus on the task at hand; the xmls tend to be rather big even with reduced css. 

Please consider adding this small functionality to your code.

If we end up choosing this plugin for our work, we'll surely end up adding more customizations to it. I'll let you know of anything we think You might find interesting.

Thanks again,
Marcin Trycz