public static class Preferences
{
#if UNITY_2019_1_OR_NEWER
    public class MarkownSettings : SettingsProvider
    {
        public MarkownSettings(string path, SettingsScope scopes = SettingsScope.User, IEnumerable<string> keywords = null)
            : base(path, scopes, keywords)
        {
        }
        // 自定义GUI
        public override void OnGUI(string searchContext)
        {
            GUILayout.Button("测试");
        }
    }

    [SettingsProvider]
    static SettingsProvider MarkdownPreferences()
    {
        return new MarkownSettings("Preferences/Markdown");
    }
#else
        [PreferenceItem( "Markdown" )]
#endif
}