This may seem to be the most naive post imaginable.

How can I type notes, assign them (automatically or by hand) to nested categories, see the categories in columns, and use custom views to see the result?

Did you ever get your reply either through pm or e-mail?

I don't understand your topic and that may be the reason why you aren't getting any replies.

This question makes sense to me - if I am right in assuming that you are referring to Lotus Agenda?
I am currently unaware of any PIM that offers similar functionality. I'd be using it if I did.

Sorry, last sentence should read "I'd be using it if I was aware of such."

Closest program thus far (to my knowledge) is ZootXT. http://www.zootsofware.com

Will do the auto assign to one or more folder/category, flexible import and yes even basic Outline functions.

There is a a bit of a learning curve, very active mailing list group (via yahoo). Worth a peek.