I also prefer to drag and drop, or what some call "side load" my files, from my actual files, not a library. For several reasons, one is to make sure that the files get into the specific SD card I want them to go to. I do not want to overload the fixed card, and only load my favorites there, trying to keep space open for the upgrades and playlists, as SD cards can get problems if overwritten too much. I now have a SD card for rock/pop, one for Jazz/Folk, and one for Classical/Holiday, and just take out the SD card and put it in my computer, and open it up on a browser. I can rename it what I want. Then I open up my music folders on my computer. click on the file, click copy, to, or drag. I find that doing more than a couple at a time take quite a while. On my computer, I keep only the new files, and ones I have not backed up yet. I then will copy files to my main storage device, a 2 TB Seagate external drive, under Music, in folders for each genre and if it is 14 bit or 24 bit quality. So I have at least 2 copies of the files, and plan to have another on the cloud when I can figure out how to access the one I have when I bought my Windows Surface.
The second reason is that it is a lot faster. I have not had problems with changing out SD cards on my PONO, although some people have. I make sure it is turned off prior to changing it. It can take up to 3 minutes or so for my 128 GB card sometimes. I have had my PONO since October 2014, and running great still, having done this since my first time, when I had no clue what files were going to which of the two SD cards in the PONO player. The only time you need PMW to load a file is if you are loading on to the fixed SD card on the PONO player.