Calibre does not use the file system to manage ebook libraries, it uses a relational database, it uses the file system as as a place to keep book format files, cover image files, and metadata backup data.
I suggest you read the detailed explanation in the following sticky thread to get an appreciation of why a database is better tool for organising something like an ebook collection than a file system alone ==>>
Want to change folder structure or file names in the Calibre library?
By default calibre only has 'columns' for the major elements of the Dublin Core spec, but via its custom column feature you can extend that in any way you want.
BR