I'd like to suggest two things that might enhance the new download history feature:
1. Similar to the OP's request, an ability to log automatically the names of all downloaded NZB root nodes in a text file, with date & time, and/or unrared filenames, and maybe directory info. Something simpler than the full log file is what I'm thinking. I like to get a quick view of what I've been leeching over the last few days and weeks, at the moment I do this manually with a batch routine (using a bit of a roundabout method, tbh). I also add comments like the OP - mainly to record which files I've replaced with propers or internals, etc. This log is purely for information purposes, the dl history takes care of dupes nicely.
2. An option to keep all entries in the Download Queue with status updates instead of automatic removal of completed files. The new cleanup button and/or timer option can do that work now, and it's nice sometimes to see what's happened to each file in the set without digging through the full log.
-Hecks