ExtraWorldFileEditWindow.xaml

<Window x:Class="ValheimSaveShield.ExtraWorldFileEditWindow"
        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:ValheimSaveShield"
        mc:Ignorable="d"
        xmlns:ui="http://schemas.modernwpf.com/2019"
        ui:WindowHelper.UseModernWindowStyle="True"
        Title="File Extension" SizeToContent="Height" Width="200" ResizeMode="NoResize" FocusManager.FocusedElement="{Binding ElementName=txtExtension}">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <TextBox x:Name="txtExtension" Margin="5" Grid.Row="0" />
        <Grid Grid.Row="1">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>
            <Button x:Name="btnOK" Content="OK" Margin="5" Grid.Column="1" Click="btnOK_Click"/>
            <Button x:Name="btnCancel" Content="Cancel" Margin="5" Grid.Column="2" Click="btnCancel_Click"/>
        </Grid>
    </Grid>
</Window>