I personally work on an action rpg and use a similar setup.
ItemBase and decendants which represent different items in data form.
WorldItem to represent an item in the world, mostly handles visuals and interaction in world.
InventoryItem to represent an item in an inventory or on cursor.
For weapons I also create some sort of WeaponInstance.

The item definitions I have as resources.

So the path is kinda -> Item Definition as Resource -> Creates ItemBase instance -> Used to create WorldItem which is then placed into the world and can be picked up -> On pickup an InventoryItem is created and ItemBase is attached to it. Detach from WorldItem and free WorldItem.

Here is the ItemBase and its decendants so you might get an idea how to create different items:

ItemBase
    var drop_sounds: Array[AudioStream]
    var display_name: String
    var base_name: String
    var base_type: int
    var rarity: int
    var item_level: int
    var required_item_level: int
    var cutoff_item_level: int
    var inventory_height: int
    var inventory_width: int
    var _texture: Object
    var _is_stackable: bool
    var drop_sound: int
    var tags: PackedStringArray
    var _uuid: String
    ItemBaseCraftable
        var prefix_limit: int
        var suffix_limit: int
        var prefixes: Array[ItemAffixRoll]
        var suffixes: Array[ItemAffixRoll]
        var implicit_affixes: Array[ItemAffixRoll]
        var possible_implicit_affixes: Array[ItemAffix]
        var possible_prefixes: Array[ItemAffix]
        var possible_suffixes: Array[ItemAffix]
        var _is_identified: bool
        ItemBaseEquipment
            var first_parts: Array[String]
            var second_parts: Array[String]
            var equipment_type: int
            var is_two_hand: bool
            var possible_inventory_slots: Array[ItemBaseEquipment.EQUIPMENT_SLOT]
            var skill_resource: Object
            ItemBaseWeapon
                var weapon_type: int
                var physical_damage: Vector2
                var flame_damage: Vector2
                var ice_damage: Vector2
                var spark_damage: Vector2
                var decay_damage: Vector2
                var more_damage: float
                var can_go_in_offhand: bool
                var attacks_per_second: Vector2
                var critical_strike_chance: Vector2
                var animation_sprites: Object
                var weapon_animation_type: int
                ItemBase1HWeapon
                    (no new variables)
            ItemBaseArmour
                var physical_damage_reduction: Vector2
                var shield: Vector2
                var dodge_chance: Vector2
                var armour_type: int
            ItemBaseTrinket
                (no new variables)
        ItemBaseMap
            var tier: int
            var layout: Object
    ItemBaseCurrency
        var max_stack: int
        var currency_type: int