Clean UI Toolkit Custom Controls with [UxmlElement] (Unity 6)

The Tip: In earlier Unity versions, creating custom UI Toolkit controls required writing boilerplate UxmlFactory and UxmlTraits classes.

How to Use: Mark custom VisualElement classes with [UxmlElement]. Expose Inspector fields inside UI Builder using [UxmlAttribute].

using UnityEngine.UIElements;

[UxmlElement]
public partial class HealthBarElement : VisualElement
{
    [UxmlAttribute]
    public int MaxHealth { get; set; } = 100;
}