Translations:Reloading and Updating Changes/25/en
From DragonMineZ Wiki
Each config file carries a configVersion (for example "2.2.0"). When it is older than the mod's version, DMZ moves the old file to config/dragonminez/oldBackup/<same path>, writes the new defaults, and merges your values back in: values you never touched take the new default, values you changed are kept, and new keys are added. The details are on How to JSON.