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.
This makes me long for the good old days when the See Also section of the Wikipedia article for recursion included a link to recursion
If you want to see humorlessness incarnate, check out the handful of people vehemently opposing reintroducing it on the talk page…