WPF Binding List

Вот такая картина

   public class Config
    {
        public String Key { get; set; }

        public String ValueConfig { get; set; }
    }
    
    
    public class ConfigTemplates : INotifyPropertyChanged
        {
            private String title;
            private List<Config> configs;
    
            public String Title
            {
                get => title;
                set
                {
                    title = value;
                    OnPropertyChanged(nameof(Title));
                }
            }
            
            public List<Config> Configs
            {
                get => configs;
                set
                {
                    configs = value;
                    OnPropertyChanged(nameof(Configs));
                }
            }
    
            public event PropertyChangedEventHandler PropertyChanged;
    
            [NotifyPropertyChangedInvocator]
            protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
            {
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
            }
        }
        
         public sealed class ApplicationViewModelContext : INotifyPropertyChanged
            {
                private ConfigTemplates selectedConfig;
        
                public ObservableCollection<ConfigTemplates> Configs { get; set; }
                            
                public ConfigTemplates SelectedConfig
                {
                    get => selectedConfig;
                    set
                    {
                        selectedConfig = value;
                        OnPropertyChanged(nameof(SelectedConfig));
                    }
                }            
        
                public ApplicationViewModelContext()
                {                   
        
                    Configs = new ObservableCollection<ConfigTemplates>()
                    {
                        new ConfigTemplates()
                        {
                            Title = "XXX",
                            
                            Configs = new List<Config>()
                            {
                                new Config {Key = $"1", ValueConfig = $@"XXX1"},
                                new Config {Key = $"2", ValueConfig = $@"XXX2"},
                                new Config {Key = $"3", ValueConfig = $@"XXX3"}
                            }
                        }
                    };
                }
        
                public event PropertyChangedEventHandler PropertyChanged;
        
                [NotifyPropertyChangedInvocator]
                private void OnPropertyChanged([CallerMemberName] string propertyName = null)
                {
                    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
                }
            }
            
            
            <Grid>
                     <Grid.ColumnDefinitions>
                         <ColumnDefinition Width="0.5*"/>
                         <ColumnDefinition Width="*"/>
                     </Grid.ColumnDefinitions>   
              
                    <ListBox Grid.Column="0" ItemsSource="{Binding Configs}" SelectedItem="{Binding SelectedConfig}">
                    <ListBox.ItemTemplate>
                        <DataTemplate>
                            <StackPanel Margin="5">
                                <TextBlock FontSize="18" Text="{Binding Path=Title}"/>
                            </StackPanel>
                        </DataTemplate>
                    </ListBox.ItemTemplate>
                    </ListBox>
                    
                    <StackPanel Grid.Column="1" DataContext="{Binding SelectedConfig}">
                        <TextBlock Text="Selected Settings"/>
                        <TextBlock Text="Title"/>
                        <TextBox Text="{Binding Title, UpdateSourceTrigger=PropertyChanged}"/>
                        
                        <-- НЕ работает --!>
                        <ListBox ItemsSource="{Binding Configs, UpdateSourceTrigger=PropertyChanged}"/>
                        
                    </StackPanel>
                    
                </Grid>

как можно вывести данные Configs

                    <ListBox ItemsSource="{Binding Configs, UpdateSourceTrigger=PropertyChanged}"/>

То есть, слева отображается Title, при нажатии на него, справа должны отобразится данные из Configs . Работает, Title отображается, но Configs отображаются не правильно.Как можно вывести Key = $"1", ValueConfig = $@"XXX1"