well "native" in this case would mean OS library. Most likely there is and you can use the UFFI to do it but I assume here you mean Morphic.
I have played around with Progress bar when I was trying to increase its size for PharoLauncher. As almost all things inside Pharo is not documented and its entangled between messages. But yeah it should be possible to animate the green bar so it bounces left and right. If my memory serves me correctly its not nothing more than a set of super simple morphs tied to announcements.��
Its that my mentality usually is if something is simple enough as an idea it does not worth wasting your time learning how a poor documented library works. I have wasted huge amounts of time trying to understand Pharo libraries and tools, so I learned the hard way.��