In particular, I am interested in a proven tool that you use with confidence for troubling shooting the cause(s) of nuisance AFCI breaker tripping.
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I wish there were a tool or tools that were capable of discriminating between harmful and benign arc signatures. . . But, today, still, after 15 years since the first AFCI requirement was published in the 1999 NEC, the ONLY way to test an AFCI breaker itself, that is UL approved, is to press the TEST button on the breaker.
Any other device is an "indicator", but not a "tester".
The AFCI breakers that self-report their previous trip experience with LED blink codes helps, somewhat, to hint to the troubleshooter what may be going on, but that is about all the help, hardware based, that exists.
If the AFCI doesn't trip, the branch circuit and attached loads are OK as of the moment that there is no trip. That is the UL supported test.
Each manufacturer's solution to the Grand Concept of AFCI is proprietary and ridiculously locked down behind secrecy. The behavior of the solutions is not the same, manufacturer to manufacturer.