Example of BadgeView with circle box using custom renderer - http://julianocustodio.com/badgeview

BadViewPage.xaml.cs

...

  <ContentPage.Content>
        <StackLayout VerticalOptions="Center">
            <StackLayout Orientation="Horizontal" HorizontalOptions="Center">
                <Label HorizontalTextAlignment="Center" Text="Notifications" FontSize="18"/>
                <local:Badge x:Name="BadgeNotifications" BoxColor="red"
                             WidthRequest="18" HeightRequest="18" 
                             VerticalOptions="Center" HorizontalOptions="Center">
                    <x:Arguments>
                        <x:Double>30</x:Double>
                        <x:Double>10</x:Double>
                    </x:Arguments>
                </local:Badge>
            </StackLayout>

            <Button Text="Add Notification" Clicked="AddNotification"/>
        </StackLayout>
    </ContentPage.Content>
    
    ...