RPGItem.cs

public static class RPGItemUtility
{
    private static readonly List<RPGItem> All = new List<RPGItem>();
    private static bool IsLoaded;
    private static TaskCompletionSource<bool> IsLoadingComplete;
    
    [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)]
    private static void Load()
    {
        IsLoadingComplete = new TaskCompletionSource<bool>();
        IsLoaded = false;
        All.Clear();
            
            
        var assetLabel = new AssetLabelReference {labelString = "Items"};

        Addressables.LoadAssetsAsync<RPGItem>(assetLabel, LoadCallback).Completed += OnCompleted;
    }

    private static void OnCompleted(AsyncOperationHandle<IList<RPGItem>> obj)
    {
        if (obj.Status == AsyncOperationStatus.Succeeded)
        {
            var list = obj.Result;
            All.Clear();
            All.AddRange(list.Distinct());
            IsLoaded = true;
            IsLoadingComplete.TrySetResult(IsLoaded);
        }
    }

    private static void LoadCallback(RPGItem task)
    { }

    public static async Task<List<RPGItem>> Events()
    {
        await IsLoadingComplete.Task;
        return All;
    }
}

[Flags]
public enum EquipmentSlot
{
    LeftHand,
    RightHand,
    Chest,
    Head,
    Feet
}

[Flags]
public enum DamageType
{
    Regular,
    Fire,
    Poison
}

[Serializable]
public class Damage
{
    public uint Amount;
    public DamageType DamageType;
}

[Serializable]
public class Heal
{
    public uint Amount;
    public HealType DamageType;
}

[Flags]
public enum HealType
{
    Regular,
    Beer
}

//The Addressables/Items folder is added to addressables list and tagged with "Items"
[CreateAssetMenu(fileName = "Addressables/Items/New RPGItem", menuName = "Assets/Item")]
public class RPGItem : ScriptableObject
{
    //Sword
    public LocalizedString LocalizedTitle;
    //A sharp weapon of death
    public LocalizedString LocalizedDescription;
    //The 2d sprite used in the UI
    public AssetReference InventoryUIAsset;
    //The 3d model dropped on the ground
    public AssetReference WorldAsset;
    public uint PurchaseValue;
    public uint SellValue;
    //None means not equippable (i.e consumable)
    public EquipmentSlot EquipmentSlot;
    //The damage this item deals
    public Damage Damage;
    //The heal this item gives
    public Heal Heal;
}

[CustomEditor(typeof(RPGItem))]
public class RPGItemEditor : Editor
{
    public override void OnPreviewGUI(Rect r, GUIStyle background)
    {
        var item = target as RPGItem;
        if (item != null)
        {
            if (item.WorldAsset != null && item.WorldAsset.IsValid())
            {
                //Draw WorldAsset
            }
            else if (item.InventoryUIAsset != null && item.InventoryUIAsset.IsValid())
            {
                //Draw InventoryAsset
            }
        }
    }
}