I think the best way to do this is create an instance of an scene and add it as a child:
anim = preload("res://winanim.scn").instance()
And in the node free that node when necessary, for example with a timer
var timer = Timer.new()
timer.set_wait_time(3) # time in secondn
There are probably other better solutions, but this one seems not that bad. You can also quit that scene with
at any point.