Apparently, importing ~/.config/kglobalshortcutsrc is enough for the shortcut to show up in the System Settings, but not enough to load the shortcut. Disabling, applying and re-enabling and applying again also doesn’t help, and neither does re-assigning to the same shortcut, which resulted in this lovely error dialog.
Wait there wasnt a Windows key since forever?
Computer keyboards have been around since at least the 70s and the Windows key only started appearing on keyboards with the release of Windows 95. I am a child of the 80s and my first 3 or 4 computers had keyboards with no Windows key.
TIL!
But to be honest, that was also pretty much before standardization. I have never seen anyone use Meta for the Alt key.