[Feature request] Add category as metadata and for filter

[update-freak]

Hi,

would be good if it would be possible to add the category of the PDF file to it's metadata.
With category I mean: Book, Lecture Slides, Scripts, Magazines, Manuals, Dissertations, etc.
At the moment I use the Tags for it, but I also want to use the Tags for the topic: KI, Programming, Fluid Mechanics, ...
And therefore the tag list is quite long and not that good structured.

[mrmn2]

I am planning to implement this in the near future.