Add a contentarea control.
MODIFY
WalletWasabi.Fluent/App.xaml
WalletWasabi.Fluent/App.xaml
<StyleInclude Source="avares://WalletWasabi.Fluent/Styles/Themes/BaseDark.xaml" />
<StyleInclude Source="avares://WalletWasabi.Fluent/Icons/Icons.xaml" />
<StyleInclude Source="avares://WalletWasabi.Fluent/Styles/Styles.xaml" />
+ <StyleInclude Source="avares://WalletWasabi.Fluent/Controls/ContentArea.axaml" />
<StyleInclude Source="avares://WalletWasabi.Fluent/Controls/Dialog.xaml" />
<StyleInclude Source="avares://WalletWasabi.Fluent/Controls/NavBarItem.xaml" />
<StyleInclude Source="avares://WalletWasabi.Fluent/Controls/NavBarTreeItem.xaml" />

ADD
WalletWasabi.Fluent/Controls/ContentArea.axaml
+<Styles xmlns="https://github.com/avaloniaui"
+ xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+ xmlns:c="clr-namespace:WalletWasabi.Fluent.Controls">
+ <Design.PreviewWith>
+ <Panel Background="{DynamicResource RegionColor}">
+ <c:ContentArea
+ Width="400" Height="200"
+ Title="Add a Wallet"
+ Caption="Type in your Wallets name and select an option below:">
+ </c:ContentArea>
+ </Panel>
+ </Design.PreviewWith>
+ <Styles.Resources>
+ </Styles.Resources>
+ <Style Selector="c|ContentArea">
+ <Setter Property="Template">
+ <ControlTemplate>
+ <DockPanel>
+ <StackPanel DockPanel.Dock="Top">
+ <ContentPresenter Name="PART_TitlePresenter" Content="{TemplateBinding Title}" />
+ <ContentPresenter Name="PART_CaptionPresenter" Content="{TemplateBinding Caption}" />
+ </StackPanel>
+ <ContentPresenter Name="PART_ContentPresenter"
+ Background="{TemplateBinding Background}"
+ BorderBrush="{TemplateBinding BorderBrush}"
+ BorderThickness="{TemplateBinding BorderThickness}"
+ ContentTemplate="{TemplateBinding ContentTemplate}"
+ Content="{TemplateBinding Content}"
+ Padding="{TemplateBinding Padding}"
+ VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
+ HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"/>
+ </DockPanel>
+ </ControlTemplate>
+ </Setter>
+ </Style>
+ <Style Selector="c|ContentArea /template/ ContentPresenter#PART_TitlePresenter">
+ <Setter Property="TextBlock.Foreground" Value="{DynamicResource TextControlForeground}" />
+ <Setter Property="TextBlock.FontSize" Value="24" />
+ </Style>
+ <Style Selector="c|ContentArea /template/ ContentPresenter#PART_CaptionPresenter">
+ <Setter Property="TextBlock.Foreground" Value="{DynamicResource TextControlForeground}" />
+ <Setter Property="TextBlock.FontSize" Value="14" />
+ <Setter Property="Opacity" Value="0.6" />
+ </Style>
+</Styles>

ADD
WalletWasabi.Fluent/Controls/ContentArea.axaml.cs
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Controls.Presenters;
+
+namespace WalletWasabi.Fluent.Controls
+{
+ public class ContentArea : ContentControl
+ {
+ public static readonly StyledProperty<object> TitleProperty =
+ AvaloniaProperty.Register<ContentArea, object>(nameof(Title));
+
+ public static readonly StyledProperty<object> CaptionProperty =
+ AvaloniaProperty.Register<ContentArea, object>(nameof(Caption));
+
+ public object Title
+ {
+ get => GetValue(TitleProperty);
+ set => SetValue(TitleProperty, value);
+ }
+
+ public object Caption
+ {
+ get => GetValue(CaptionProperty);
+ set => SetValue(CaptionProperty, value);
+ }
+
+ protected override bool RegisterContentPresenter(IContentPresenter presenter)
+ {
+ var result = base.RegisterContentPresenter(presenter);
+
+ switch(presenter.Name)
+ {
+ case "PART_TitlePresenter":
+ case "PART_CaptionPresenter":
+ result = true;
+ break;
+ }
+
+ return result;
+ }
+ }
+}

Add a contentarea control.