My apologies. I usually do not post on these kinds of websites.
Before RockBox, when I wanted to transfer music, I just dragged and dropped two file folders - i think it was like "workoutsongs" and "partycds" that each had you know, maybe 40 songs in them. That worked.
After installing RockBox, I tried the same thing. First, I just tried to drag and drop the files, not in a folder in the MUSIC folder. Then I thought that they might already have to be in a folder so I made a folder to put them all in (sansadec30) and tried that. After doing that a few times, I realized that the folder was hidden and tried two other folders. In .rockbox, I tried to move the files 'sansadec30' to just within there and also in the ".wps" file. I also tried to move the folder into .tps.
I hope that is clear enough.