You can add a HTML snippet with the following JavaScript:
<selectorforyourbutton>.onClick = function() {
var objDiv = <selectorforyourmessagecontainer>;
objDiv.scrollTop = objDiv.scrollHeight;
}
You might need some timeout though to make sure it's only triggered after the message appears.
It's not possible to trigger it from your microflow, since there's only limited client-side updates that can be triggered from there (open page, close page, show pop up message, etc...)
Is there an update for this on Native? I see Listviews have a scrollToEnd() function, but that does not seem to be triggerable. I will add the idea in the portal. Hack ideas are welcome ;-).