The XmlExplorer is a clone from a CodePlex project back in 2009: https://xmlexplorer.codeplex.com/
The GitHub project here applies the MVVM pattern and unlocks therefore advanced theming and configuration features (re-usability patterns).
The project is currently in Alpha state (do NOT expext a fully developed application), but the available refactoring is very interesting.
A tool for editing Xml is XmlNotepad https://github.com/Microsoft/XmlNotepad