Secret structure of the kicad_sym library files?

Are any documents or specifications available on the internal keywords and structure used inside the kicad_sym library files? I see no mention of this in the the forums nor in the manual. If the file format is undocumented then can anyone point me to any specific source code which may contain comments or be helpful? Thanks.

It should be here: Symbol Library File Format | Developer Documentation | KiCad
But there is not much over there.

Looking at the sourcecode for the schematic symbol editor may be a good start. It’s a relatively small piece of KiCad, and the part that reads and writes the files should be easy to isolate:

That’s absolutely amazing, thanks! I’m making some extra symbols and hope to have them merged into the KiCad library.

The “Symbol Section” section links to SYMBOL_DEFINITION in the schematic file format doc, which seems to be complete at first glance.

Hmm, oddly enough the Color attribute does not work with Circle within Symbols. I suppose it may be reserved for footprints or some other use.

I suspect it works in the nightlies (6.99), but not in the stable release (6.0.5).