S42 undocumented parameters

The S42 tag seems to be able to do a fair bit more than is documented – off the top of my head, [[S42:0:sec-cat]] will return the numerical ID of the security category assigned to the event; however, "sec-cat" is not listed as a parameter in the online help documents.

I am attempting to reference the "Event Registration Limit" for a TeamRaiser I'm creating, but searching through the script and DOM nor the info in the API seems to be elucidating what the parameter name might be. It seems like it SHOULD be referrable – "registration-limit-type", the setting just before it, is a thing – but I've tried dozens of permutations, synonyms, and abbreviations of "event", "registration", "limit", and "number" and I'm coming up empty-handed.

If anyone happens to know what the parameter for this value might be and could let me know, I'd appreciate it. Also, a number of S-tags seem to have their own built-in "help" function, but [[S42:0:help]] returns a null string and [[S42:help]] returns, oddly, "$10,000.00". Is there a way to make S42 dump all its acceptable parameters?