The Flash animation makes nodes appear at the begin keyframe and disappear at the end keyframe. This is done via the visibility of nodes and not via their transparency.
See also animations: Appear, Disappear, Show, Shown, Hide, Hidden, Pulse
First, choose nodes that you want to show and hide.
Then, double-click on the Flash animation effect in the Animation panel of the Animator.
This animation has 4 keyframes:
Move the keyframes of the animation as needed.
Note: You can always move the keyframes of the animation.
You can change how the parameters are interpolated between the frames by modifying the Easing curve.