Puthujjanas sure are obsessed with karma. Do not forget that the goal of the dhamma, expressed in terms of karma, is to end karma, not ''to know the precise workings of the karma'', not ''precise workings of the karma+ending karma''. THe only goal is to end karma.
Even if you manage to know the ''precise workings of the karma'', you still begin the path by relying, hour after hour, less and less on what is conditioned, typically karma, vedana, vinanna, birth, ageing, contact, and so on in order to base your action on something else than karma. And knowing the 'precise workings of the karma'' is not part of the method to end karma.
That being said, the buddha claims that indeed there are things that must be known
[5] "'Kamma should be known. The cause by which kamma comes into play
should be known. The diversity in kamma should be known. The result of
kamma should be known. The cessation of kamma should be known. The
path of practice for the cessation of kamma should be known.' Thus it
has been said. In reference to what was it said?
"Intention, I tell you, is kamma. Intending, one does kamma by way of
body, speech, & intellect.
"And what is the cause by which kamma comes into play? Contact is the
cause by which kamma comes into play.
"And what is the diversity in kamma? There is kamma to be experienced
in hell, kamma to be experienced in the realm of common animals, kamma
to be experienced in the realm of the hungry shades, kamma to be
experienced in the human world, kamma to be experienced in the world
of the devas. This is called the diversity in kamma.
"And what is the result of kamma? The result of kamma is of three
sorts, I tell you: that which arises right here & now, that which
arises later [in this lifetime], and that which arises following that.
This is called the result of kamma.
"And what is the cessation of kamma? From the cessation of contact is
the cessation of kamma; and just this noble eightfold path — right
view, right resolve, right speech, right action, right livelihood,
right effort, right mindfulness, right concentration — is the path of
practice leading to the cessation of kamma.
"Now when a disciple of the noble ones discerns kamma in this way, the
cause by which kamma comes into play in this way, the diversity of
kamma in this way, the result of kamma in this way, the cessation of
kamma in this way, & the path of practice leading to the cessation of
kamma in this way, then he discerns this penetrative holy life as the
cessation of kamma.
"'Kamma should be known. The cause by which kamma comes into play...
The diversity in kamma... The result of kamma... The cessation of
kamma... The path of practice for the cessation of kamma should be
known.' Thus it has been said, and in reference to this was it said.
Nibbedhika Sutta -- Penetrative (AN 6.63)
just like sanna, feeling, and all the other stuff which are conditioned should be know , their arising and their cessation.
In one word, puthujjanas and non-arhants must strive to know all this. In this sutta, the buddha does not say the method to know all those things. This sutta is about the goal expressed in terms of knowledge. This sutta is about the discrimination of teachings: there a teachings which are not the dhamma and there are teachings which are the Dhamma explanation. The buddha says all the things and only the things that constitute a ''Dhamma explanation''
SO to know karma, you must find another sutta. In the first sermon of the buddha, the buddha claims he directed his citta to know karma and rebirth [meaning, the diveristy of karma and the result of karma]
it turns out that even for other puthujjanas, knowing karma is about getting the citta into samadhi:
Here is a little exposition about samadhi.
The Samādhi Bhāvanā Sutta (A 4.41) mentions four uses or benefits of
mental concentration (samādhi), 1 namely, (1) for happiness here and
now; (2) for the divine eye 2 (clairvoyance and knowledge of the
working of karma); (3) mindfulness and clear comprehension; and (4)
spiritual liberation.
...
“The perception of light” (āloka,saññā) here is prescribed for the attainment of “knowledge and vision,” defined as the divine eye (that is, the psychic power of clairvoyance and the knowledge of the working of karma and rebirth). However, the perception of light is also efficacious in a more mundane way, such as the overcoming of drowsiness, as prescribed in the Pacalā Sutta (A 7.58). In psychological terms, the perception of light is also useful in keeping the mind “bright” in a positive sense, which pre-vents or cures depressive and negative mental states
The Samādhi Bhāvanā Sutta (A 4.41)
