I've a question to the translation-files in NX10. For example "\LOCALIZATION\translations\german". There are many .txt-files the user can extend them for own terms, e.g. for user defined operations or user_cycles or messages out of the post. I've done it and it works.
But what's the scenario for the updating the files? If I get new translation-files with a new MP I don't have a chance to update the files in an easy way. I have to do it with handwork.
The NX API allows you to create your own text translation file. Have a look at the LoadTranslationFile and TranslateString2 methods (and basically all of the other functions provided in the UFText namespace).
If, however, you modify the files provided with the NX install, you will need to maintain them yourself. I'd suggest saving a copy of your modified version in a location that won't be over-written by an NX patch; after installing the patch you can use a text file merge tool to reapply your edits.