I am a little surprised that there isn’t better support for Dropbox, is this because it is blocked in China? Some levels of integration from simplest to more difficult. I’m surprised that the Essential level is missing while level 2 has been available to other apps for several years now.
Essential Use the default dropbox API to grant access to one folder (for privacy!) and have this synced folder show up as a folder in the MN browser with its contents, subfolders, etc. The user could then organize their folder as they wish on dropbox and access it in different devices to add/manage documents.
This would make library management so much easier and bring MN into a much larger app ecosystem with organic modes of integration.
Level 2 Bring basic two-way synchronization already present for years in other pdf reading apps (like Documents) where basic markup like highlights and annotations are saved to the the original pdf and are accessible across devices outside of MN.
Level 3 Bring study export options to the already integrated dropbox folder.