By accident I just hit the key combination <meta>+= and suddenly my screen is very very unpleasant to work; the KDE desktop was too big to fit in the monitor area! As this just occured after upgrading to KDE-5.39 I expected something was wrong in the new kde packages. After using different desktops (icewm, gnome), logging into other KDE user desktops none of them showed the issues. So it really seemed to be a KDE thing in my user environment. Spending some time, moving away files and putting them back one by one I was in the end able to restore the situation. Using the backup I have; in the end it appeared that the ~/.config/kwinrc contained the culprit. The setting InitialZoom was set to 1.2 [Effect-Zoom] InitialZoom=1.2 With help of https://forums.opensuse.org/showthread.php/527862-After-upate-KDE-screen-no-longer-fits-in-monitor-screen I'm now aware that is a zoom factor, and can be reverted using the combinatie <meta>+- May I asked for a popup window that shows up when those (type of) buttons are activated, at least when the <meta>+- is activated. The popup should inform the user, that the zooming can be undone using <meta>+- The popup should have the option "do you want to see this window next time". When it is not possible to tell the user how to undo the zooming as the unzoom combination is configurable, ask the user: "are you sure to zoom in? Do you want to continue?" Zooming can be undone with the correct key combination. I hope I get my message across. Make sure that users that are hitting this key combination by accident (in my case I was looking for another key combination), are informed what is going to happen, that it can be undone, and especially where to look for information about this feature (desktop zooming). I consider this a bug, although the software is working correctly, but it results in a desktop that is no longer useful and I had to use my backup to restore the old situation!
Perhaps it is possible to show something on the desktop that zooming has been activated, including a zoom back to normal button at the top of screen (for example). Even the user enabled "no longer show this popup message", show it again when the zooming functionality has not been used for a long time (1 year). One might not remember that zooming has been enabled and that it can be restored using for example <meta>+- I hope that usability issue gets a good followup.
While I understand your concern, I don't think this is necessary. We have this shortcut by default for now almost 10 years and you are the first one to report this as a bug. To me this means that it is not worth the effort.
That's too bad. In that case I've remove the key assignment: To prevent this from happening again, I removed the meta key combination; (kde) system settings -> accelerator keys -> global keys -> system settings -> zoom in Remove it from there.