Я думаю, вам придется повторно шаблонировать DataGridRow для этого. Немного поигрался с ним и получил результат, показанный ниже. Надеюсь, это то, что вы имели в виду
Видимость "крест" привязывается к свойству IsCrossed
<DataGrid ...>
<DataGrid.RowStyle>
<Style TargetType="{x:Type DataGridRow}">
<Setter Property="Background" Value="{DynamicResource {x:Static SystemColors.WindowBrushKey}}"/>
<Setter Property="SnapsToDevicePixels" Value="true"/>
<Setter Property="Validation.ErrorTemplate" Value="{x:Null}"/>
<Setter Property="ValidationErrorTemplate">
<Setter.Value>
<ControlTemplate>
<TextBlock Foreground="Red" Margin="2,0,0,0" Text="!" VerticalAlignment="Center"/>
</ControlTemplate>
</Setter.Value>
</Setter>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type DataGridRow}">
<Border x:Name="DGR_Border" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" SnapsToDevicePixels="True">
<SelectiveScrollingGrid>
<SelectiveScrollingGrid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
</SelectiveScrollingGrid.ColumnDefinitions>
<SelectiveScrollingGrid.RowDefinitions>
<RowDefinition Height="*"/>
<RowDefinition Height="Auto"/>
</SelectiveScrollingGrid.RowDefinitions>
<DataGridCellsPresenter Grid.Column="1" ItemsPanel="{TemplateBinding ItemsPanel}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
<DataGridDetailsPresenter Grid.Column="1" Grid.Row="1" SelectiveScrollingGrid.SelectiveScrollingOrientation="{Binding AreRowDetailsFrozen, ConverterParameter={x:Static SelectiveScrollingOrientation.Vertical}, Converter={x:Static DataGrid.RowDetailsScrollingConverter}, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}" Visibility="{TemplateBinding DetailsVisibility}"/>
<DataGridRowHeader Grid.RowSpan="2" SelectiveScrollingGrid.SelectiveScrollingOrientation="Vertical" Visibility="{Binding HeadersVisibility, ConverterParameter={x:Static DataGridHeadersVisibility.Row}, Converter={x:Static DataGrid.HeadersVisibilityConverter}, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}"/>
<Path Name="cross" Grid.ColumnSpan="2" Visibility="Collapsed" Data="M0,0 L1,1 M0,1 L1,0" Stretch="Fill" Stroke="Black" StrokeThickness="1" />
</SelectiveScrollingGrid>
</Border>
<ControlTemplate.Triggers>
<DataTrigger Binding="{Binding IsCrossed}" Value="True">
<Setter TargetName="cross" Property="Visibility" Value="Visible"/>
</DataTrigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</DataGrid.RowStyle>