So, yeah, I could have saved several hours of work if, when I tried to use the "import XML" option, #KWallet had just popped up a dialog saying "This feature requires en existing wallet into which to import. Either open one or create a new one."
Offering to create a new wallet if you don't already have one would also have been helpful, but just that information alone could have saved all that time.
Alternatively, they could have put all the features that work with an open wallet into a menu-entry called "wallet", or similar, and have it greyed out when you don't have an open wallet selected.
On the internet, everyone knows you're a cat — and that's totally okay.