It sure would be convenient if BetterZip was able to accept files from one open BZ archive to be dragged and dropped into another open BZ archive. As it stands now, if I want to add a file from one BZ archive to another, I first have to extract the file of interest to disk. Once that's done, I then can add the extracted file to the other BZ archive. I then delete the temporary file extracted to disk.

I mention this because I've been able to do Stuffit archive-to-archive drag-and-drop for years now without first having to create an intermediate, temporary file on disk -- just so that I can get one file from one archive into another archive.