Just did a quick test with “export as XML” and “import XML” from KWalletManager and that worked for me.
As I already have “kdewallet” I have created a new wallet with a different name and imported it there, though.
Exported it with only the old wallet open and selected, imported it only the new wallet open and selected. I got a folder XXX entry XXXX already exists (for some unknown reason as at that point nothing was open where that already exists) and selected “ignore all” and all the entries appeared in the new wallet regardless.
You may or may not modify the wallet name <wallet name="kdewallet"> tag in the XML file, but that was not necessary in my test.
Important: Be careful with the XML as it contains everything unencrypted, save that only to a secure place and securely fully delete after it is no longer needed.