sure - you can do it all with cloud folders, if you are ignoring the warnings all over this forum about the dangers of using calibre library in a cloud or on NAS . One day you will break it and get little sympathy.
meanwhile see Chaley's post here
https://www.mobileread.com/forums/sh...ight=card+oreo
post 2
"It is worth noting that starting in Nougat (Android 7), Google has totally broken sharing files between apps.
Later this year CC will be forced to hand copies of books to reader apps instead of pointing the reader app at CC's local copy. I know that this is terrible but there is zero I can do about it. If I don't implement this stupid system then later in the year I must stop releasing CC updates."