iCloud keychain items can't be exported or added to new, empty keychain using Keychain Access
I can't temporarily move my iCloud Keychain items into a new keychain for troubleshooting. The underlying issue appears to be that Safari for Mac doesn't seem to be able to use items in the iCloud keychain, and I'm trying to fix it. In other words, if I search for passwords in Safari for Mac that are easily found among passwords on my iPhone, the search results on the Mac are empty.
Anyway, selecting all the iCloud keychain items in Keychain Access and trying to export them doesn't work, because Export Items is grayed out in the File menu. Trying to copy and paste even a single item from the existing iCloud keychain to a new, empty one I created just to troubleshoot results in this error message:
I've started a case with Apple Support, because my Silicon MacBook Pro 16" is still under warranty, but communication for this sort of tedious issue is, uh, well, difficult. Thanks.