Is there a way of having the rokdd app do a proper backup that includes the entire directory? Presumably that is the point of having an app that "automatically exports" your library when new items are added, no?
Zotero export isn't for backing up, so by definition that's not what those add-ons (there are a few) are for. They're more appropriate for, say, keeping a BibTeX file used by another program up to date with your library.
The way to have a backup — of Zotero or anything else — is just to use a backup system that does automated incremental backups of your files — and ideally your entire hard drive, as Time Machine does on macOS.
(You can of course also use Zotero sync, which uploads changes after every change, but that's not really a proper backup either. It will help you if your hard drive dies or you lose your laptop, but if you delete something accidentally, the deletion is immediately uploaded as well.)
No, the main goal of that add-on is to keep a database -- in particular, but not necessarily, a bibtex database file -- in sync with the Zotero library. If you want automated back-ups, don't use a Zotero add-on. Just make sure that whatever automated back-up tool you're using (on Mac that'd be time machine, but I think Window's built-in tool does this too, as do the tools that ship with most external hard disks) includes the Zotero data folder and that's all. See https://www.zotero.org/support/zotero_data#backing_up_your_zotero_library
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The way to have a backup — of Zotero or anything else — is just to use a backup system that does automated incremental backups of your files — and ideally your entire hard drive, as Time Machine does on macOS.
(You can of course also use Zotero sync, which uploads changes after every change, but that's not really a proper backup either. It will help you if your hard drive dies or you lose your laptop, but if you delete something accidentally, the deletion is immediately uploaded as well.)
If you want automated back-ups, don't use a Zotero add-on. Just make sure that whatever automated back-up tool you're using (on Mac that'd be time machine, but I think Window's built-in tool does this too, as do the tools that ship with most external hard disks) includes the Zotero data folder and that's all. See https://www.zotero.org/support/zotero_data#backing_up_your_zotero_library