It would be nice if LibreOffice supported Office365 OneDrive for Business/Sharepoint Online.
There is currently no OneDrive for Business client for Linux, but if LibreOffice supported ODfB file access directly, it would help co-operation with Microsoft Office users.
There is a REST API for Onedrive and Onedrive for Business:
Setting to NEW.
Any idea how much effort this would need? Could it be done with an addon? I am even thinking of paying someone to do this if it won't be a very big (expensive) job.
Hmm. Is OneDrive for Business somehow very different from the regular OneDrive? OneDrive support is still unfinished: bug 62437
If you think it would be all the same, you could close your report as a duplicate of bug 62437
They are actually quite different. ODfB is actually more close to SharePoint. But last year Microsoft released the new OneDrive REST API 2.0 that works for both services. I have no idea which API the now-broken and disabled OneDrive integration functionality in LibreOffice utilizes.
I also tried using the SharePoint support in LibreOffice, but didn't get it working, likely because ODfB supports only forms based authentication.
I would also mention that in ODfB, files shared by others to you are not synced to the local folder. Microsoft Office accesses them via WebDAV.
I think the best course of action would be make LibreOffice support form-based authentication on WebDAV. Then one would be able to enter the URL of the document to LibreOffice and open it for editing.