When activating the sync feature of Windows 10/Onedrive one is asked which of the three directories Desktop, Documents and Pictures should be synced between devices.
How do I add other directories to this list, like Videos or Downloads or misc?
OneDrive has the particularity that it will only sync files from its folder,
located at %UserProfile%\OneDrive
.
Nevertheless, you may trick it to think that your other folders are contained as subfolders using symbolic links.
To sync any folder to OneDrive, open a Command Prompt and enter this command:
mklink /j "%UserProfile%\OneDrive\Folder-Name" "Full path of source folder"
The source folder will now appear in OneDrive under the name of "Folder-Name" and be synced automatically.