Rated 5 out of 5 stars
I guess klint also contacted me. I am the author of CompactHeader. He suggests to add two buttons to convert the selected mail (in the message list pane) into a event/task, like it is done in the context menu. I implemented these two buttons and submitted a patch to lightning itself. See https://bugzilla.mozilla.org/show_bug.cgi?id=575413
If this bug were not implemented you are very welcome to add the source code to your addon. On the other hand, you might try to get your buttons added to lightning itself. Your buttons should really be part of the lightning.