Simple CustomPropertyDrawer to show/hide properties based on an Enum or Boolean value

ConditionalDisplayDrawer.cs

using System;
using System.Collections.Generic;

#if UNITY_EDITOR
using UnityEditor;
using UnityEditor.UIElements;
using UnityEngine.UIElements;

[CustomPropertyDrawer( typeof(TestProp))]
public class TestPropDrawerUIE : PropertyDrawer
{
    public override VisualElement CreatePropertyGUI( SerializedProperty property )
    {
        // Create foldout for sub-properties
        var container = new Foldout{text = property.displayName};
        
        // Create fields
        var FieldBool1   = new PropertyField(property.FindPropertyRelative( "Bool1" ));
        var FieldFloat1  = new PropertyField(property.FindPropertyRelative( "Float1" ));
        var FieldInt1    = new PropertyField(property.FindPropertyRelative( "Int1" ));
        var FieldMyEnum1 = new PropertyField(property.FindPropertyRelative( "MyEnum1" ));
        var FieldString1 = new PropertyField(property.FindPropertyRelative( "String1" ));
        var FieldListe1  = new PropertyField(property.FindPropertyRelative( "Liste1" ));
            
        // Add fields to the container.
        container.Add(FieldBool1);
        container.Add(FieldFloat1);
        container.Add(FieldInt1);
        
        container.Add(FieldMyEnum1);
        container.Add(FieldString1);
        container.Add(FieldListe1);
        
        // Register change callback on boolean field
        FieldBool1.RegisterCallback<ChangeEvent<bool>>( e =>
        {
            // Toggle visibility as needed
            var visible_style =  e.newValue ?
                new StyleEnum<DisplayStyle>(DisplayStyle.Flex) :
                new StyleEnum<DisplayStyle>(DisplayStyle.None);
            
            FieldFloat1.style.display = visible_style;
            FieldInt1.style.display   = visible_style;
        });
        
        // Register change callback on an enum field
        // Enum fields changes are typed as string
        FieldMyEnum1.RegisterCallback<ChangeEvent<string>>( e =>
        {
            // so we need to parse the value
            if( Enum.TryParse(e.newValue, out MyEnum coucou) )
            {
                // Toggle visibility as needed
                var visible_style =  coucou == MyEnum.ABC ?
                    new StyleEnum<DisplayStyle>(DisplayStyle.Flex) :
                    new StyleEnum<DisplayStyle>(DisplayStyle.None);
            
                FieldString1.style.display = visible_style;
                FieldListe1.style.display  = visible_style;
            }
            
        });
        
        return container;
    }
}
#endif

public enum MyEnum
{
    ABC = 0,
    DEF = 1
}

[Serializable]
public class TestProp
{
    // bool driven properties
    
    public bool   Bool1;
    // these properties are shown only if Bool1 = true
    public float  Float1;
    public int    Int1;
    
    // enum driven properties
    
    public MyEnum MyEnum1;
    // these properties are shown only if MyEnum1 = MyEnum.ABC
    public string    String1;
    public List<int> Liste1;
}

Note that it uses the UIToolkit implementation and won't work with IMGUI