Since categories have a hierarchical structure, it would be good to have an option, when you click on a higher level category in the right-hand panel in references and notes, to match things that are associated with a lower level category.
For example: I am in linguistics, so I have languages as categories, arranged into language families. For example, I have a category Germanic, and under it are the categories English, German, Norwegian, etc. I would like to be able to click on Germanic and have all of the references/notes that are linked with English, German, Norwegian, etc. come up as matches.
+ 1
I second this. Also, it would be good to be able to select categories by typing in a search widow as there can be many and manual selection really slows things down.