This is a nice application to test or write a mission file. One of the things I liked is the ability to feedback my XML based on XML Schema file (XSD), it is like a rule file that describes what can be defined in the file and what is not. It takes time to construct a good "XSD" file and I was working on one, until I accidentally override it.
In any case, I'll upload soon the XSD file based on Mission-X v2.0x rules, you can update it if something is missing or correct/modify it to make it better. Then you can send me your version and I'll update the master file on this site.
Until I'll prepare the files, Here is an example: