如何在WPF中为Tab控件提供自定义形状？

我在WPF中制作了一个应用程序，需要在其中使用TabControl在目录之间进行切换。但是由于设计目的，我的Tab项的内容在同一水平线后跟Tab项标题。

这是我的Mainwindow.xaml的代码

<Grid Width="635" HorizontalAlignment="Left" Height="458" VerticalAlignment="Top" Margin="0,61,0,0" >



            <TabControl Margin="-1" BorderThickness="0" Background="#222222" >
               
                <TabItem   Style="{StaticResource TabItemDefaults}"                            Header="File manager"  FontSize="10" Foreground="#efefef" Margin="5,0,0,0" Width="97" Height="20"   FontFamily="Segoe UI" UseLayoutRounding="True" TextOptions.TextFormattingMode="Display"                        >

                    <Grid>
                        <Label Name="Folder" Content="Folder:"  FontSize="10" Foreground="#efefef"   Height="20" Width="40"  Margin="-571,-367,0,0"   FontFamily="Segoe UI" UseLayoutRounding="True" TextOptions.TextFormattingMode="Display"                                  />
                        <Button Name ="FolderSelect"                               Width="532" HorizontalAlignment="Left" VerticalAlignment="Top"  Height="33" Margin="85,17,0,0"     Background="#1a1a1a"   
                            
                            materialDesign:ShadowAssist.ShadowDepth="Depth0" materialDesign:RippleAssist.Feedback="Transparent" BorderThickness="0"  UseLayoutRounding="True"
                            
                            ></Button>
                        <Label Name="ShowFolders" Content=".." Margin="-479,59,0,0"  Background="#1a1a1a"  Width="168" Height="373"  Foreground="#efefef" ></Label>


                        <Button
    Style="{StaticResource MaterialDesignRaisedButton}"
                           
                            
    Width="65" HorizontalAlignment="Left" Height="25" Background="#FF403D3D" Margin="16,292,0,0" 
                            
                           
    ToolTip="Resource name: MaterialDesignRaisedButton">
                            <materialDesign:PackIcon Kind="PlusThick" />

                        </Button>

                        <Button
    Style="{StaticResource MaterialDesignRaisedButton}"
    Width="65" HorizontalAlignment="Left" Height="25" Background="#FF403D3D" Margin="82,292,0,0" 
    ToolTip="Open output folder">
                            <materialDesign:PackIcon Kind="FolderUpload" />
                        </Button>

                        <Label Content="Video recordings:" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="269.2,-22,0,0" Foreground="#efefef"  FontSize="10"  FontFamily="Segoe UI" UseLayoutRounding="True" TextOptions.TextFormattingMode="Display" />
    
                    </Grid>    
                </TabItem>
                <TabItem   Style="{StaticResource TabItemDefaults}"                                           Header ="Preview"   FontSize="10" Foreground="#efefef" Width="67" Height="20" Margin="-8,0,0,0"  FontFamily="Segoe UI" UseLayoutRounding="True" TextOptions.TextFormattingMode="Display"                  >

                    <Grid>
                        <CheckBox Content="Draggable mode" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="520,-22,0,0"     Width="110"                                    />


                    </Grid>

                </TabItem>

            </TabControl>


        </Grid>

Tab控件和Tab项均由我在App.xaml中声明的控件模板制成。

这是我在App.xaml中分别声明的Tab控件的代码-

<Style  TargetType="{x:Type TabControl}"  x:Key="TabControlDefaults"  x:Name="NewTabcontrol" >
                <Setter Property="OverridesDefaultStyle"
          Value="True" />
                <Setter Property="SnapsToDevicePixels"
          Value="True" />
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="{x:Type TabControl}">
                            <Grid KeyboardNavigation.TabNavigation="Local">
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="Auto" />
                                    <RowDefinition Height="*" />
                                </Grid.RowDefinitions>
                                <VisualStateManager.VisualStateGroups>
                                    <VisualStateGroup x:Name="CommonStates">
                                        <VisualState x:Name="Disabled">
                                            <Storyboard>
                                                <ColorAnimationUsingKeyFrames Storyboard.TargetName="Border"
                                                Storyboard.TargetProperty="(Border.BorderBrush).
                    (SolidColorBrush.Color)">
                                                    <EasingColorKeyFrame KeyTime="0"
                                         Value="#FFAAAAAA" />
                                                </ColorAnimationUsingKeyFrames>
                                            </Storyboard>
                                        </VisualState>
                                    </VisualStateGroup>
                                </VisualStateManager.VisualStateGroups>
                                <TabPanel x:Name="HeaderPanel"
                    Grid.Row="0"
                    Panel.ZIndex="1"
                    Margin="0,0,4,-1"
                    IsItemsHost="True"
                    KeyboardNavigation.TabIndex="1"
                    Background="Transparent" />
                                <Border x:Name="Border"
                  Grid.Row="1"
                  BorderThickness="1"
                  CornerRadius="2"
                  KeyboardNavigation.TabNavigation="Local"
                  KeyboardNavigation.DirectionalNavigation="Contained"
                  KeyboardNavigation.TabIndex="2">
                                    <Border.Background>
                                        <LinearGradientBrush EndPoint="0.5,1"
                                   StartPoint="0.5,0">
                                            <GradientStop Color="{DynamicResource ContentAreaColorLight}"
                              Offset="0" />
                                            <GradientStop Color="{DynamicResource ContentAreaColorDark}"
                              Offset="1" />
                                        </LinearGradientBrush>
                                    </Border.Background>
                                    <Border.BorderBrush>
                                        <SolidColorBrush Color="{DynamicResource BorderMediumColor}"/>
                                    </Border.BorderBrush>
                                    <ContentPresenter x:Name="PART_SelectedContentHost"
                              Margin="4"
                              ContentSource="SelectedContent" />
                                </Border>
                            </Grid>
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>

这是我在App.xaml中分别声明的Tab项的代码-

<Style TargetType="{x:Type TabItem}" x:Key="TabItemDefaults" x:Name="NewTabitem"   >

                <Setter Property="Foreground" Value="#bababa" />

                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="{x:Type TabItem}">
                            <Grid x:Name="Panel"    ClipToBounds="true" SnapsToDevicePixels="true" KeyboardNavigation.TabNavigation="Local"                                                      >
                                <ContentPresenter x:Name="ContentSite"
                                        VerticalAlignment="Center"
                                        HorizontalAlignment="Center"
                                        ContentSource="Header"
                                        Margin="10,2"/>
                            
                            
                            </Grid>
                            
                           
                            <ControlTemplate.Triggers>


                                <Trigger Property="IsMouseOver" Value="True">
                                    <Setter Property="Foreground" Value="Black"/>
                                </Trigger>



                                <Trigger Property="IsSelected" Value="True">
                                    <!--    <Setter TargetName="Panel" Property="Background" Value="LightSkyBlue"  /> -->
                                    <Setter Property="HeaderTemplate">
                                        <Setter.Value>
                                            <DataTemplate>
                                                <TextBlock Text="{TemplateBinding Content}">

                                                    <TextBlock.TextDecorations>
                                                        <TextDecoration  PenOffset="4" PenOffsetUnit="Pixel" >
                                                            <TextDecoration.Pen>
                                                                <Pen Brush="#673ab7" Thickness="4" />
                                                            </TextDecoration.Pen>
                                                        </TextDecoration>
                                                    </TextBlock.TextDecorations>

                                                </TextBlock>
                                            </DataTemplate>
                                        </Setter.Value>
                                    </Setter>


                                </Trigger>
                                <Trigger Property="IsSelected" Value="False">
                                    <Setter TargetName="Panel" Property="Background" Value="#212121" />
                                    <Setter Property="Foreground" Value="WhiteSmoke"/>

                                </Trigger>

                              
                            </ControlTemplate.Triggers>
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>

我的问题是复选框（我给一个红色圆圈）不能正常运行。我知道主要原因是该复选框位于“选项卡控件”的选项卡面板之外。但出于我的应用程序的设计目的，我必须将其放置在此处。

因此，如何为Tab控件的选项卡面板提供自定义形状，以便将内容元素完美地停靠在所需的位置。