Highlights:

The new Link tool has been designed to allow quickly
creating navigation links (e.g. DITA xref and link
elements).

While very convenient to use when editing a monolithic
document, the Link tool really shines when it comes to
creating navigation links in the context of a modular
document (modular DocBook book, DITA map or bookmap, etc).

More information:
http://www.xmlmind.com/xmleditor/changes.html