One of the most asked for enhancements is to be able to add comments in the center pane. You can now do that in the latest snapshot:
To add a Note item, right click in the center pane and select Note from the menu. If you right click on an existing item, the Note item will be placed pointing to that item, if there is space.
You can change the comment, arrow direction and color of the Note in the right pane when it is selected.
You can get the snapshot here (if you have visited the page before, make sure to refresh to get the latest version of the page):
The direct links to the downloads are:
Please try it and let us know if you have any problems.