Declares that a class can be instantiated from UXML and contain UXML attributes. The UxmlSerializedData includes a generated UxmlSerializedData.CreateInstance method that uses the default constructor. You can use the UxmlCreateInstanceMethodAttribute to replace the default behaviour and provide your own creation method.
A UXML object is a class that can be instantiated from UXML and contain UXML attributes. By utilizing the UxmlObjectReferenceAttribute attribute, you can use a UXML object to associate complex data with a field, surpassing the capabilities of a single UxmlAttributeAttribute.