SUMMARY

In Windows as in the other Linux distro that I have used, such as Ubuntu, Xubuntu, lubuntu, Mint, among others not KDE, when you open some icons like the internet connection icon, the volume, language, etc. icon, in the sector of notifications of the panel (or bar), it is not necessary to go to the icon of that opened window (notifications) to close it, since just doing left click to any empty space of the bar (or panel) or even the desktop, it is minimized or closed (I don't know exactly how some call it this process, to minimize or to close the notification).
It is a matter of practicality: if I am very focused on the subject I am working on, what I least want is to concentrate on minor issues such as going to place the mouse pointer on the icon to close it ... more when the icons are small.
But also yes in KDE you can minimized (close) the notifications opened (volume, internet connection, etc) if you left click anywhere on the desktop ... Then, why is is possible to minimize if you click on the desktop and not at any point on the panel and not in any open space of the bar (panel)? I am used to working like this on Windows, and I see that other non-KDE distros also work the same way, so that is why I was surprised that KDE does not work the same way.