MainWindow.xaml

<Window x:Class="TreeViewScrolling.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:local="clr-namespace:TreeViewScrolling"
        mc:Ignorable="d"
        Title="MainWindow"
        Height="450"
        Width="800">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="*" />
        </Grid.ColumnDefinitions>

        <TreeView x:Name="tv"
                  Grid.Column="0"
                  VirtualizingPanel.IsVirtualizing="True"
                  ItemsSource="{Binding}">
            <TreeView.ItemTemplate>
                <HierarchicalDataTemplate DataType="{x:Type local:ItemViewModel}"
                                          ItemsSource="{Binding Children}">
                    <TextBlock Text="{Binding Id}" />
                </HierarchicalDataTemplate>
            </TreeView.ItemTemplate>
        </TreeView>

        <StackPanel Grid.Column="1">
            <Button Content="Position 1"
                    Click="Button_Click" />

            <Button Content="Position 2"
                    Click="Button_Click_1" />
        </StackPanel>
    </Grid>
</Window>