Item Flags are used to show/hide certain elements of an Item's tooltip information.
As of 1.21, there are many new experimental flags for the component system.

Example config format:

item-flags:
  - HIDE_ATTRIBUTES
  - HIDE_ENCHANTS

Common Item Flags:
    HIDE_ENCHANTS              - Hide enchantments from tooltip
    HIDE_ATTRIBUTES            - Hide attributes like Damage, Armor, etc.
    HIDE_UNBREAKABLE           - Hide the "Unbreakable" text
    HIDE_DESTROYS              - Hide what blocks the item can break
    HIDE_PLACED_ON             - Hide where the item can be placed
    HIDE_ADDITIONAL_TOOLTIP    - Hide potion effects, book info, firework info, map tooltips, banner patterns
    HIDE_DYE                   - Hide dye color from leather armor
    HIDE_ARMOR_TRIM            - Hide armor trim info

Extended Item Flags (1.20.5+ component system, may be experimental):
    HIDE_CUSTOM_DATA
    HIDE_MAX_STACK_SIZE
    HIDE_MAX_DAMAGE
    HIDE_DAMAGE
    HIDE_CUSTOM_NAME
    HIDE_ITEM_NAME
    HIDE_ITEM_MODEL
    HIDE_LORE
    HIDE_RARITY
    HIDE_ENCHANTMENTS
    HIDE_CAN_PLACE_ON
    HIDE_CAN_BREAK
    HIDE_ATTRIBUTE_MODIFIERS
    HIDE_STORED_ENCHANTMENTS
    HIDE_DYED_COLOR
    HIDE_CHARGED_PROJECTILES
    HIDE_BUNDLE_CONTENTS
    HIDE_POTION_CONTENTS
    HIDE_POTION_DURATION_SCALE
    HIDE_SUSPICIOUS_STEW_EFFECTS
    HIDE_WRITABLE_BOOK_CONTENT
    HIDE_WRITTEN_BOOK_CONTENT
    HIDE_TRIM
    HIDE_DEBUG_STICK_STATE
    HIDE_ENTITY_DATA
    HIDE_BUCKET_ENTITY_DATA
    HIDE_BLOCK_ENTITY_DATA
    HIDE_INSTRUMENT
    HIDE_PROVIDES_TRIM_MATERIAL
    HIDE_OMINOUS_BOTTLE_AMPLIFIER
    HIDE_JUKEBOX_PLAYABLE
    HIDE_PROVIDES_BANNER_PATTERNS
    HIDE_RECIPES
    HIDE_LODESTONE_TRACKER
    HIDE_FIREWORK_EXPLOSION
    HIDE_FIREWORKS
    HIDE_PROFILE
    HIDE_NOTE_BLOCK_SOUND
    HIDE_BANNER_PATTERNS
    HIDE_BASE_COLOR
    HIDE_POT_DECORATIONS
    HIDE_CONTAINER
    HIDE_BLOCK_STATE
    HIDE_BEES
    HIDE_LOCK
    HIDE_CONTAINER_LOOT
    HIDE_TOOL
    HIDE_FOOD
    HIDE_CONSUMABLE
    HIDE_USE_REMAINDER
    HIDE_USE_COOLDOWN
    HIDE_ENCHANTABLE
    HIDE_REPAIRABLE
    HIDE_REPAIR_COST
    HIDE_CREATIVE_SLOT_LOCK
    HIDE_TOOLTIP_STYLE
    HIDE_TOOLTIP_DISPLAY
    HIDE_DEATH_PROTECTION
    HIDE_EQUIPPABLE
    HIDE_GLIDER
    HIDE_DAMAGE_RESISTANT
    HIDE_ENCHANTMENT_GLINT_OVERRIDE
    HIDE_INTANGIBLE_PROJECTILE
    HIDE_MAP_COLOR
    HIDE_MAP_DECORATIONS
    HIDE_MAP_ID
    HIDE_MAP_POST_PROCESSING
    HIDE_WEAPON
    HIDE_BLOCKS_ATTACKS
    HIDE_BREAK_SOUND

Entity Variant Flags (for spawn eggs, etc.):
    HIDE_VILLAGER_VARIANT
    HIDE_WOLF_VARIANT
    HIDE_WOLF_SOUND_VARIANT
    HIDE_WOLF_COLLAR
    HIDE_FOX_VARIANT
    HIDE_SALMON_SIZE
    HIDE_PARROT_VARIANT
    HIDE_TROPICAL_FISH_PATTERN
    HIDE_TROPICAL_FISH_BASE_COLOR
    HIDE_TROPICAL_FISH_PATTERN_COLOR
    HIDE_MOOSHROOM_VARIANT
    HIDE_RABBIT_VARIANT
    HIDE_PIG_VARIANT
    HIDE_COW_VARIANT
    HIDE_CHICKEN_VARIANT
    HIDE_FROG_VARIANT
    HIDE_HORSE_VARIANT
    HIDE_PAINTING_VARIANT
    HIDE_LLAMA_VARIANT
    HIDE_AXOLOTL_VARIANT
    HIDE_CAT_VARIANT
    HIDE_CAT_COLLAR
    HIDE_SHEEP_COLOR
    HIDE_SHULKER_COLOR

Legacy Flag Names (for older versions):
    HIDE_POTION_EFFECTS        - Now HIDE_ADDITIONAL_TOOLTIP or HIDE_POTION_CONTENTS

Note: Many extended flags are marked @Experimental in Spigot and may change.
For most use cases, the common flags (HIDE_ENCHANTS, HIDE_ATTRIBUTES, etc.) are sufficient.
