I regularly enable and disable the Wifi network adapter. So, I set the shortcut Meta+N to open the network applet (from there it is fast to reach the wireless checkbox). I now noticed that after a few days that shortcut binding disappears as if it has never been set. I have not figured out yet what situation makes the binding disappear. I set the shortcut by right-click on the applet icon > Network Settings... > Keyboard Shortcuts.
This is not an issue in plasma-nm, I would guess kglobalaccel is responsible.
A bunch of applet-shortcut-related bugs got fixed recently and I suspect this one did too. It works for me perfectly now in Plasma 5.21. Can you check to see if it's fixed for you too?
Let's close it. By the way, there is no possibility anymore to assign a shortcut for the "Networks" applet. :-)
You're right! That is worthy of another bug report. I know why it happens and can fix it, but the fix will result in a slightly ugly UI, sadly.
Bug report: https://bugs.kde.org/show_bug.cgi?id=434249