One thing that comes to mind when revealing existing text would be to set up a material mask. Then use the widget retainer. Altering the mask bit by bit would reveal the text underneath.
Could work, but sounds somewhat rigid and a tad fiddly, though.
vs next frame:
Here it is not even UE’s fault. It’s doing its best. I’d hate to write code that checks whether a line of text fits into the box, so I’d rather have a mask, tbh.
There may be a clever solution to this, who knows.