There are a lot of tools for xml-editing, currently I use the following ones, but i am interested if anyone knows different (and probably better) ones? I prefer open source software, but also commercial software is interesting:

https://notepad-plus-plus.org/ - https://www.altova.com/de/xmlspy.html - http://www.xmlcooktop.com/ - https://marketplace.eclipse.org/content/eclipse-xml-editors-and-tools-0