https://learn.microsoft.com/pt-br/windows/windows-app-sdk/api/winrt/microsoft.ui.xaml.media.animation.fillbehavior?view=windows-app-sdk-2.0
FillBehavior Enum (Microsoft.UI.Xaml.Media.Animation) - Windows App SDK | Microsoft Learn
Specifies how a Timeline behaves when it is outside its active period but its parent is inside its active or hold period.
media animationwindows appenummicrosoftui