https://learn.microsoft.com/en-us/uwp/api/windows.ui.xaml.frameworkelement.focusvisualmargin?view=winrt-28000
FrameworkElement.FocusVisualMargin Property (Windows.UI.Xaml) - Windows apps | Microsoft Learn
Gets or sets the outer margin of the focus visual for a FrameworkElement.
propertywindowsuixamlapps