Hey guys!
Bad news first. The translated string key editor was never intended to be used for localization purposes. We use a separate pipeline for that, taking into account everything for VO, translation, multiple languages, etc. Converting that editor to support such localization is not feasible. Especially not since we iterate on it ourselves between titles. So a hard no on that.
As to finding a way to allow modding of loca, we could look into allowing you to add localization files in your mod folders and let the system also check your mod files instead of only the Data\Localization files. But you would have to make the localization files yourself, by for example copying the English one and altering the language. Does this sound agreeable?
Sincerely,
Kevin