Most likely you should use the XML Parser functions in LabVIEW to build your custom XML. These functions/VIs are located in Function Palette>>File I/O>XML>>XML Parser.
In the Example Finder, search for XML, and then open the Generate XML String with Parser API.vi example to see how to use the API.
I love this library as it generates a very nice and still readable XML-code (in comparison to the "flatten to XML" LabVIEW primitive).
But I now stumbled about the "decimal point" error that is already mentioned in this thread elsewhere, i.e. that GXML uses the "decimal point" settings of your OS to create and parse floating point numbers. It should always create floating point number with a dot as the decimal point!
Of course that is something easily fixed since none of the VIs is password protected.
But it would even be easier if if the source code would be available on github like many other System Engineer Libraries so that we can create our own versions and give them back to the community.