はじめに

上記の記事の手順を踏むことで ContentSizeFitter の Inspector に
HorizontalFit と VerticalFit を同時に変更するボタンを追加できます

ソースコード

using UnityEngine;
using UnityEngine.UI;

namespace UnityEditor.UI
{
    [CustomEditor(typeof(ContentSizeFitter), true)]
    [CanEditMultipleObjects]
    /// <summary>
    ///   Custom Editor for the ContentSizeFitter Component.
    ///   Extend this class to write a custom editor for an ContentSizeFitter-derived component.
    /// </summary>
    public class ContentSizeFitterEditor : SelfControllerEditor
    {
        SerializedProperty m_HorizontalFit;
        SerializedProperty m_VerticalFit;

        protected virtual void OnEnable()
        {
            m_HorizontalFit = serializedObject.FindProperty("m_HorizontalFit");
            m_VerticalFit = serializedObject.FindProperty("m_VerticalFit");
        }

        public override void OnInspectorGUI()
        {
            serializedObject.Update();
            EditorGUILayout.PropertyField(m_HorizontalFit, true);
            EditorGUILayout.PropertyField(m_VerticalFit, true);
            
            var fitter = target as ContentSizeFitter;

            using ( new EditorGUILayout.HorizontalScope() )
            {
                if ( GUILayout.Button( "Unconstrained" ) )
                {
                    Undo.RecordObject( fitter, "Unconstrained" );

                    fitter.horizontalFit = ContentSizeFitter.FitMode.Unconstrained;
                    fitter.verticalFit   = ContentSizeFitter.FitMode.Unconstrained;
                }
                if ( GUILayout.Button( "Min Size" ) )
                {
                    Undo.RecordObject( fitter, "Min Size" );

                    fitter.horizontalFit = ContentSizeFitter.FitMode.MinSize;
                    fitter.verticalFit   = ContentSizeFitter.FitMode.MinSize;
                }
                if ( GUILayout.Button( "Preferred Size" ) )
                {
                    Undo.RecordObject( fitter, "Preferred Size" );

                    fitter.horizontalFit = ContentSizeFitter.FitMode.PreferredSize;
                    fitter.verticalFit   = ContentSizeFitter.FitMode.PreferredSize;
                }
            }
            
            serializedObject.ApplyModifiedProperties();

            base.OnInspectorGUI();
        }
    }
}