Custom property attribute to make ReadOnly variables in Unity Inspector

ReadOnlyAttribute.cs

using UnityEngine;

public class ReadOnlyAttribute : PropertyAttribute
{
}

ReadOnlyDrawer.cs

using UnityEditor;
using UnityEngine;

[CustomPropertyDrawer(typeof(ReadOnlyAttribute))]
[CanEditMultipleObjects]
public class ReadOnlyDrawer : PropertyDrawer
{
	public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
	{
		EditorGUI.BeginProperty(position, label, property);

		bool enabledState = GUI.enabled;
		GUI.enabled = false;
		EditorGUI.PropertyField(position, property, label, true);
		GUI.enabled = enabledState;

		EditorGUI.EndProperty();
	}

	public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
	{
		return EditorGUI.GetPropertyHeight(property);
	}
}

how about adding this to make it work with UI Toolkit? :)

[CustomPropertyDrawer(typeof(ReadOnlyAttribute))]
[CanEditMultipleObjects]
public class ReadOnlyDrawer : PropertyDrawer {
public override void OnGUI(Rect position, SerializedProperty property, GUIContent label) {
	EditorGUI.BeginProperty(position, label, property);

	bool enabledState = GUI.enabled;
	GUI.enabled = false;
	EditorGUI.PropertyField(position, property, label, true);
	GUI.enabled = enabledState;

	EditorGUI.EndProperty();
}

public override float GetPropertyHeight(SerializedProperty property, GUIContent label) {
	return EditorGUI.GetPropertyHeight(property);
}

public override VisualElement CreatePropertyGUI(SerializedProperty property) {
	PropertyField propertyField = new PropertyField(property);
	propertyField.SetEnabled(false);
	propertyField.style.opacity = 0.5f;
	return propertyField;
}