ItemManager helps you to keep your custom items organized. With all of these item keys to manage (display, lore, enchantments, attributes, etc), it can be hard to keep track of your items. Sometimes, you need a custom crafting item to be used in recipes, sometimes you need random "scrap" items to be saved... ItemManager helps you to solve that.
ItemManager interfaces with my other plugins. This is great for setting up crafting recipes for your custom armor from ArmorMechanics and weapons in WeaponMechanics.