Libraries-External USB Drives-not showing up-even though properties are showing them

Added folders on external usb-drives to Libraries
Later, removed drives (rightclick taskbar button, safely remove drives)
Drives powered off
Shut down/Reboot pc
Powered on the drives

Folders do not show up in the library.

Okay, I may understand that, because of they were removed, etc.

However, rightlick on the library folder, properties, the folders are there alright.
But apparently the properties do not matter anymore, after a reboot.

Now, to add the folders again, I need to first remove them from the list.

Out of curiosity: is this the only method? Or is there not a more elegant way?
Is it not possible to have the folders 'auto detected' in the library once they are available again?
(meaning: Windows detects the drives - why not shouldn't Library check the availability of the folders
in its properties pane? Maybe this is outside Opus?)

Thanks

Do they show up in File Explorer's view of the libraries?

I'm not sure that Libraries support removable drives at all, at the Windows/OS level.

Weird...
I again did exactly the above, removing drives, shutting down, etc.
After reboot, switched on the drives again and now they are displayed in the Library (both under Windows Explorer and Opus).
No idea why they didn't in the first place.
Anyway, forget the above.
Seems sometimes non explainable things happen. . .

=

My guess is Libraries aren't designed for drives that come and go, but it might still work sometimes and not others, just by luck really.

I'm not sure what Microsoft's exact recommendations are, but I know they try to prevent you adding network drives to Libraries (even though they work reasonably well, in my experience, as long as you don't rely on indexing). It wouldn't surprise me if the same was true for removable drives.