However, it is unfortunate that most of the snbt files related to quests are made in a form that is difficult and inconvenient to translate. When modpack creators create snbt files, localization will be much easier if they don’t make them in hard-coded form, but insert only keys in the snbt file and separate text values into en_us.json.

​https://www.reddit.com/r/feedthebeast/comments/qllnpq/how_to_translate_quests_in_a_modpack_and_my/