Exstora - Built-in quick note: save ideas, contacts, interesting facts
Altova XMLSpy - The XMLSpy XML Editor is a powerful tool for editing XML and related technologies. It is the only XML Editor with patented SmartFix validation, enterprise-grade editors, converters, debuggers, and code generators.
wikidPad - wikidPad is an application for storing thoughts, ideas, todo lists, contacts, or anything else that user can think of to write down.
Oxygen XML Editor - Oxygen XML Editor provides a comprehensive suite of XML authoring and development tools.
footnote - A beautiful, fast, and simple note taking app in the style of elementary
Liquid Studio - XML Tools Provider: XML Studio - Graphical XML Schema Editor.