No, there isn't anything like that - you'd need to expose the SGEventMgr stuff and provide a Nasal/Cppbind API for that.
I once came up with a set of C++ patches doing that, but it didn't pick up much momentum back then.
But this sort of thing will definitely require a few C++ changes, it's trivial to do and could be hugely helpful when troubleshooting Nasal/Canvas issues - as a matter of fact, it could even help understand other callback-related issues (think the infamous effect cache leaking listeners like crazy)
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