A Microsoft file hosting and synchronization service.
Unfortunately that's not possible. It is the case with all cloud drives. The files need to be in OneDrive folder in order for OneDrive to know those are the ones that need to be synced to the cloud.
I've been using OneDrive for years. This is my workaround. I don't use OneDrive's folder backup feature in the settings. I want my own desktop, documents, pictures, etc., to be on my local computer with local paths.
However, I create my own folders in OneDrive folder. And I save my files/folders more intentionally to those folders in OneDrive when I need them backed up. It works well for me this way.