Translation/localisation does not happen via the translated string editor. The translated string editor merely allows for defining key/value pairs of strings that later on could be localised.
The localisation process itself is quite inflexible at this time, and does not allow for defining custom localised strings in mods, unfortunately.
You can only translate the main game in your own language should you wish to do so, by extracting english.xml from the game's pak files (not sure which it is in), renaming it to your own language, and then translating the strings in this file.
We realise this is a big limitation, but it is extremely unlikely this will be fixed for DOS2 as it would require a lot of changes to the engine.
