The new(ish) OneDrive API docs talk about multiple drives:
/drives List Drives available to the authenticated user.
However I only have a single (default) drive for my account. I can't find any info about how to create additional drives, or whether this is even possible at the moment. Maybe you get the option somewhere if you buy extra storage or use OneDrive for Business? Having said that this says:
The /drives/{drive-id} syntax is not supported for OneDrive for Business. You should always use the default drive syntax: /drive/.
Is it possible to create additional drives (manually or via the API) and if so how?
Unfortunately it is not possible to create additional drives.