I download a lot of different things from the same couple of newsgroups. So for me, applying a category to a download based on the newsgroup-name doesn't really work. I would love to be able to use keywords instead. In that case, for instance, I could assign my 'ps3' games downloads to the proper (games) category. And my UFC downloads to my 'MMA category'. No essential feature, but quite handy!
I assume you mean scanning for keyword in the NZB filename?
If so, there are ways of embedding the category in the filename.
"{{games}My game.nzb" will put "My game.nzb" in the queue under category "games".
Also when using the watched folder, you can use subfolders named after your categories.
You assumed correctly I appreciate the help and suggestions but it would not work for me because I use nzbStatus plugin for firefox that sends the .nzb directly to sab without user intervention (without first saving the .nzb to disk). I would like to automate the downloading process as much as possible.
I could stop using nzbStatus and start saving nzbfiles manually in the appropriate watch(sub)folder but that would not be more efficient than my current method of manual assigning categories to downloads.