A number of times, using Windows 8.1, I have tried to make certain OneDrive folders "available online only" using the appropriate right-click drop down menu within the file explorer. However, nothing seems to happen. There is no reassuring confirmation message and the space is still occupied on my had drive. The only way I'm certain I'm not hallucinating my "clicking" action is the brief appearance of an hour glass next to the mouse but nothing else happens.
This is not an illusion; I have checked the disk space usage in "This PC" before and after selecting the option and even downloaded a disk space analyzer (WinDirStat) to confirm my suspicion. The option in the menu does not appear to induce any subsequent action - it's just a clickable joke mocking me with the indignant hope of saving disk space by using cloud storage.
Note: the process in Windows 10 has never given my any trouble. It's only the 8.1 version.