It is independent of the installed Warcraft 3, it depends on the files in Data.
Your problem should be that you are trying to translate between 2 Data-sets which were not created using the same Ruleset.
You have to create 2 new Data-sets using Language Creator.jar based on the same Rule-Set. One for you Language used in World Editor and one for the target Language.
That software requires WorldEditStrings.txt from both languages. Nowadays one could get them using cascviewer reading the blizzard's online storage war3.w3mod:_locales\xxxxx.w3mod:ui\worldeditstrings.txt.
But I think world editor is buggy, in reforged, right now it allways is using English-locals.