This is only to inform you. The upcoming ODF 1.4 specification has in part 3 a new description for the <draw:marker>
element. That is the file markup for what is called “arrow head”, “line ending”, “arrow style” or “arrow ending” in the Draw guide . The spec contains some illustrations. The new text and the illustrations might be useful for improving the Draw guide.
You can get the current draft of the spec from https://github.com/oasis-tcs/odf-tc/tree/master/docs/odf1.4