The saved levels ARE stored as individual files. Each saved level has its own file with exactly 84kb of size. Inside each file, there are constant-sized arrays for level names, block placement and object placement, so most things are pretty easy to figure out what is what, and they are every reverse-engineer's dream. I found all this because I was researching the level files a while ago to find the IDs of the new objects. I was able to successfully copy levels around from one SD card to another. The only issue per say is that you can't have two files with colliding Level Slot IDs.
Based on this knowledge, I believe that creating a home-grown level sharing server/website for loadiine users is totally plausible, and I was even thinking of doing it, but I lack the proper motivation to do so.
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Actually, allow me to be more expecific:
Each level actually has their own folder, and there are actually 2 files for the levels (one for the normal level, and one for the sublevel), one file with the PCM recorded sound, and 2 thumbnail files.
As long as you copy them to different Level Slot ID folders, like course010 and course011, they should work.