I have the same problem when scanning, sending to, and sending by mail, a new notebook is always created directly. Apparently no default notebook can be selected. Which is a pity. But I think this is a mistake. I can't imagine that they intentionally disabled this feature ;-)
And every time I send something to evernote via Windows Explorer or scanner, the message in EN appears: "Importprocess completed...."
This message is also very annoying, can you add an option to hide it? In the old app this message did not exist.