Thank you very much for this post! I draw a lot of diagrams and have used PowerPoint instead of Keynote because I could not find this feature! This is tremendous.
It looks like Apple has some work to do to play catch up with Microsoft but this makes the charts usable where they were not without this feature.
I want to be able to select or control the type of connection as I can in PowerPoint. Sometimes I want 90 degree angles in my connection arrows. I also like being able to select a connector that has the arrow configuration that I want to use when I apply the connector. I see you can use the inspector - graphics to customize the end style, but this is pain.
Thank you for your post and letting us know about this hidden feature. For me, this makes Keynote useable for the first time.