Hello!

I would like to use part of my desktop for conky only. In other words, when I maximize a window I don't want it to cover a specific part of screen. I have successfully set maximum window size (right click on windows' toolbar ---> more actions ---> special window settings ---> size & position ---> maximum size). The problem is, that when I drag it to top of my screen its position depends where i drop it - sometimes parts of window are out of the screen. How can I fix this?

Thank you in advance for all help.

You do not want to restrict the maximum window size but the screen area, this is done by struts.
Afaik conky can only set them by "own_window_type Panel", for plasma you've to add an invisible panel - kwin does not support WM wide struts.