Stylus Studio
www.stylusstudio.com/download-xml-editor.html?gclid=CKLw-JGyw7kCFcwWMgod6nIA1A
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
Stylus Studio X15 XML Enterprise Suite is an advanced XML Integrated Development Environment (XML IDE) consisting of hundreds of powerful XML tools in one all-inclusive suite, and high-performance Java & .NET components to design data integration applications.