Hello. Are there any alternative notification managers for KDE Plasma? I've heard about Colibri. Is there anything else?

There are two methods which ship with KDE, and the 3rd party Colibri:

1) Plasma Notifications applet. These appear above your system tray usually, and can do either notifications or job status and is the default.
2) Classic. In the absence of any notification applet or Colibri, a fallback is used which displays notifications in a style similar to how KDE 3 did this. Jobs will be displayed in dialogs, and notification messages will appear in popups at the top of the screen. After removing any notification applets, you need to logout and back in again for this to take full effect.
3) Colibri.

Thank you for your answer. I actually asked this question because of one very annoying problem Plasma Notifications applet: when a notification appears (http://i.imgur.com/Y7Hxi8g.png) and I press "cross" to close it, it closes, but a sign of new notification (http://i.imgur.com/VdBlfnL.png) doesn't disappear. And Colibri doesn't provide notification for processes like archivation and copying. Can you give a piece of advice, please?

Hmm, the behaviour you are indicating definitely seems to be a bug to me. Does hovering over the applet trigger a tooltip which indicates it believes there may be pending notifications for you to check?

With regards to Colibri: I don't think it is designed to do that unfortunately. You could try keeping the main notifications applet around for the job based notifications however, and disable the regular notifications part of it and use Colibri for that instead though.