Does Cryptomator work with dropbox smart-sync and "online-only" files?

to clarify, when you open a vault, everything in it will begin downloading from the cloud (Dropbox) to your disk. There is no way to mark some items as “online” only and others as “local”? (I am on windows)

Any help or solutions would be appreciated!

The online/offline file management is done by the Dropbox app. But thanks to cryptomator, Dropbox has no clue about your single files. So you cannot say „I want to have those files offline, and others from my vault only online“.

But if you configure your complete Dropbox to use files on demand, that should work for vault files as well. I am not using Dropbox, but googledrive and OneDrive, and there the files on demand function works like a charm with the cryptomator vaults.