UI Toolkit Serializable Id

SerializableId.cs

using System;
using UnityEngine;

/// <summary>
/// A generic serializable GUID.
/// </summary>
[Serializable]
public struct SerializableId<T> : IComparable<SerializableId<T>>, IEquatable<SerializableId<T>>, ISerializationCallbackReceiver
{
    [SerializeField] private string _guid;
    public Guid Value { get; private set; } 

    public SerializableId(Guid newGuid)
    {
        Value = newGuid;
        _guid = Value.ToString();     
    }
    
    public static SerializableId<T> New() => new SerializableId<T>(Guid.NewGuid());

    public void OnBeforeSerialize()
    {
        _guid = Value.ToString();
    }

    public void OnAfterDeserialize()
    {
        if (Guid.TryParse(_guid, out var value))
            Value = value;
        else
            Value = Guid.Empty;
    }

    public int CompareTo(SerializableId<T> other) => Value.CompareTo(other);
    public bool Equals(SerializableId<T> other) => Value.Equals(other.Value);

    public override bool Equals(object obj)
    {
        if (ReferenceEquals(null, obj)) return false;
        return obj is SerializableId<T> other && Equals(other);
    }

    public override int GetHashCode() => Value.GetHashCode();
    public override string ToString() => Value.ToString();
    
    public static bool operator ==(SerializableId<T> a, SerializableId<T> b) => a.CompareTo(b) == 0;
    public static bool operator !=(SerializableId<T> a, SerializableId<T> b) => !(a == b);
}

SerializableIdPropertyDrawer.cs

using System;
using UnityEditor;
using UnityEditor.UIElements;
using UnityEngine.UIElements;

[CustomPropertyDrawer(typeof(SerializableId<>))]
public class SerializableIdPropertyDrawer : PropertyDrawer
{
    public override VisualElement CreatePropertyGUI(SerializedProperty property)
    {
        var container = new VisualElement();

        var guidProperty = property.FindPropertyRelative("_guid");
        var guidField = new PropertyField(guidProperty);
        guidField.SetEnabled(false);
        container.Add(guidField);

        var generateButton = new Button();
        generateButton.text = "Generate";
        generateButton.clicked += () =>
        {
            var guid = Guid.NewGuid().ToString();
            guidProperty.stringValue = guid;
            guidProperty.serializedObject.ApplyModifiedProperties();
        };
        container.Add(generateButton);

        return container;
    }
}

UsageExample.cs

[Serializable]
public class Item
{
    [SerializeField] private SerializableId<Item> _id;
}

public class ItemList : ScriptableObject
{
    [SerializeField] private List<Item> _items;
}