popon

Popon allows you to pop text on a window, what we call a popon.
Popons are window-local and sticky, they don't move while
scrolling, and they even don't go away when switching buffer, but
you can bind a popon to a specific buffer to only show on that
buffer.

If some popons are annoying you and you can't kill them, do M-x
popon-kill-all to kill all popons.