This discussion of exporting has helped me realize something I never paid attention to even in the Legacy client: the enex file does NOT track what NOTEBOOK notes were in! For those who knew that already, you can move on. (And yep, PinkElephant mentioned it above.) For those like me who never considered that, and its implications, you may want to read on (if you do use lots of notebooks and a hierarchy of them).
With the discussion here of how we could export one notebook at a time in the new UI, it made me wonder how that differed from my years of using the Legacy app's ability to select and export "all notes".
I just checked (in such an enex created in the old client) and I see now that in the xml underlying the enex format, it's simply got each note (in HTML format). There is no indication of what notebook each note was in. I never considered that THAT "metadata" would not also be exported.
In fact, there's NO mention in the enex of notebook names at ALL, so not only do you lose what notes were in what notebooks, you also have no backup of any representation what notebooks you had, or what stacks, or any hierarchy to notebooks.
I'm sure some will say, "dude, that's all the export ever was". I'm just saying I didn't even think to confirm that until this discussion led me to wonder.
Again, I HOPE that among the improvements in the new UI is a "true" export with even just notebook metadata. (And sure, others will wonder also about tags, favorites, saved searches, and more.)
Others may argue we should "just backup the exb file" (what EN processes as out evernote db), as it has "everything". And sure, if one just wants to restore it for recovery within EN, that works. But some of us are indeed wanting a "backup" for the sake of perhaps taking our notes (and their structure) to use with another apps. And I'm not aware that other apps yet import from the (binary) exb file.
I just never realized until today how it would be impossible to retain that relationship or note to notebook (or notebook hierarchy), in any more based on having saved the enex as an export. (I'm sure some will be wanting to point out how they knew this and have lamented it, and perhaps it's been discussed in other forum threads here. Sorry, I don't read them all. I came to this one today in tripping over more things in the new client, and wanting to "export all" from the new client, only to find out how hard it is.)
And I do realize others will point out how this is all just more of the evil plan the Evernote team has to "lock us in". Maybe they do. Maybe they will be reconsidering btter export capabilities. A boy can have dreams.