With the rise of JSON, many developers have abandoned XML. However, legacy enterprise systems, Android strings.xml , Microsoft Office Open XML ( .docx ), and SOAP APIs still run the world. The remains the standard for quick, reliable XML editing.
If you don't have it yet, the installation is straightforward via the built-in Notepad++ Plugin Manager : How do I format XML in Notepad++? - Stack Overflow xml tools plugin for notepad