ChangedJSON-tag storage to NBT storage, your items will be authomatically converted on runtime from json-tag scheme to nbt scheme. NBT scheme was applied to add 1.8-1.20 versions and changes all logic around storage. If this system will be quite stable, it will be introduced as a free version's feature in V3
Warning create a backup of your configs. The change is breaking, there is no compatibility for configs created/edited on V2.9 for V2.8