Thanks @johnnydecimal and @_FJ for your reply and the link. It’s not a clear cut sollution for what I was trying to accomplish. But it did convince me to drop trying to combine it. So problem solved anyway.
For me the strength of PARA is that it has different levels of actionability. Or more to the point (for me). Everything in P needs my attention first, then everything in A, then in R and the last A I can neglect.
But I don’t like moving files around and also, what I need to work, is actually kept in my Calendar and Todo app. And the PARA categories were collecting subfolders in such a fast pace that I needed extra structure, which I was looking for by using the JD-system. Learned from this post: Cataloging, Classification, Information Science, PKMs and YOU!
But combining, doesn’t really workout, for me. So. I will drop the PARA system and merge Areas and Resources.
Using more of the JD-system will also strenghten my opinion that it was a good decision to buy the JohnnyDecimal book. 