PowerToys/src/core/Microsoft.PowerToys.Settings.UI/Controls/DummyUserControl.xaml

<UserControl
    x:Class="Microsoft.PowerToys.Settings.UI.Controls.DummyUserControl"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:Microsoft.PowerToys.Settings.UI.Controls"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:winui="using:Microsoft.UI.Xaml.Controls"
    mc:Ignorable="d"
    d:DesignHeight="300"
    d:DesignWidth="400">

    <Grid>
        <StackPanel Background="LightCoral">
            <TextBlock>This is a simple custom UWP control</TextBlock>
            <Rectangle Fill="Blue" Height="100" Width="100"/>
            <TextBlock Text="{x:Bind XamlIslandMessage}" FontSize="50"></TextBlock>
            <winui:RatingControl />
        </StackPanel>
    </Grid>
</UserControl>