Yeah, it was a nice method. Sonar has the capability to read in the registry hook as long as it's there. It was basically something that people making editors would support, and they'd just appear in Sonar. But I think like anything non-standardised, support for it has waned over the years.
To be fair to Cakewalk, this dates back
at least to 1996, and this kind of functionality didn't appear in other daws for years. Several still don't do anything like it.