MainWindow.xaml

<Window x:Class="NestedCollectionEditor.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:syncfusion="http://schemas.syncfusion.com/wpf" 
        xmlns:local="clr-namespace:NestedCollectionEditor"
        mc:Ignorable="d" WindowStartupLocation="CenterScreen"
        Title="PropertyGrid - Nested Collection Editor" Height="650" Width="800">
    <Window.DataContext>
        <local:ViewModel/>
    </Window.DataContext>
    <Grid>
        <syncfusion:PropertyGrid Height="200"
                                 Width="350" 
                                 SortDirection="{x:Null}" 
                                 PropertyExpandMode="NestedMode"
                                 x:Name="propertyGrid"
                                 SelectedObject="{Binding DemoProduct}" />
    </Grid>
</Window>