I have a few folders of notes that are from previous - and somewhat traumatic - times. I don't want to see the notes all the time in search results, because they're a little bit triggering, but I don't want to delete them either.
So here's what I did:
1. Export the troubling notebook as .enex file
2. Create new notebook called "Archived Notebooks"
3. Create a new note, named after the exported notebook.
4. Drop the .enex file into that note as a file attachment.
The notes no longer appear in search, they no longer appear in the notes list, but they are still safely stored in Evernote and can be restored by properly reimporting the .enex file.
Just my $0.02 and a little tip. Hope it helps some of you!