Modifiers adds randomly-assigned modifiers to tools, armor, and curios (if installed - Forge only), that add small buffs to the player. These modifiers are assigned when the item is first equipped or held. Modifiers can be re-rolled using the vanilla smithing table, using the repair material for that item. (Items with no repair material currently can't be re-rolled, this is a planned feature)
The old 1.14 version is curios only, and uses XP to re-roll modifiers instead.
Want to discuss the mod or give feedback? Join my mod dev discord.