BaseKeyValueData.cs

public abstract class BaseKeyValueData<TKey, TValue> : ScriptableObject
{
    [SerializeField] private TValue _default;
    [SerializeField] private List<DataPair<TKey, TValue>> _dataPairs;

    public IEnumerable<DataPair<TKey, TValue>> Pairs => _dataPairs;

    public TValue GetValue(TKey key)
    {
        foreach ((TKey key1, TValue value) in Pairs)
            if (key1.Equals(key))
                return value;
        return _default;
    }
}