Using a memory card as a device

[Jellby]

Is there any way to use a memory card, as a device?

I have a card in my reader, but I usually take it out of the reader and put it in my computer's card reader to manage the books. I would like calibre to treat this card as if it were inside the device (which, in my case, means copying the thumbnails).

I can do something similar by configuring the card reader as a "user defined" device, but that doesn't copy the thumbnails (or at least not in the correct format).

And additionally, is there any way to restrict which folders are read from a device/card when searching for books?

[kovidgoyal]

Write a custom device plugin, you can do whatever you want in it, including copying thumbnails.