An informational tooltip in Plasma is an item that shows extra informations for items such as task items, and is a single entity, moving along what you want to know more of, rather than magically appear out of nowhere (that’s the kind of “magic” the human brain doesn’t like).
A problem with Plasma tooltips was that they tried to animate themselves, that is usually not a good idea on X11, due to its old async architecture.
But KWin to the rescue! if we want a smooth animation of both the position and the size of the tooltip, the compositor is the place where to do it.
With its scripting user interface, it was even possible to implement it completely in JavaScript.
You can see it in this video taskbar tooltips animating and resizing/morphing in a similar way Windows 7 does.

Btw, the animations in he video looks way less smooth than are in reality, due how terrible screencasting is under X11, but for that:

Wayland will fix it!