You can add 5 type of accounts to OnlyOffice: google box dropbox onedrive Ownloud/webdav.
Each one of these systems has a native file sync tool for all major OS for offline access to files.
Yet onlyoffice doesnt support the concept of file symc natively, i am surprised this want a big need early on and still doesnt exist in a sophisticated product.
When i am on an airplane and want to work on a project related document because i just had a great idea, i will have to wait because i didn't previously think to download the document to my pc
Is there a reason why the concept is online only with no automated offline support?