Yes. It is necessary to clearly understand these fundamental concepts.
You asked: “Now also “kāyasaṅkhāro, vacīsaṅkhāro, cittasaṅkhāro” are mentioned. That is explained as “kāyasañcetanā kāyasaṅkhāro, vacīsañcetanā vacīsaṅkhāro, manosañcetanā cittasaṅkhāro”. What is that in real life? It seems it is every action that is not abhisankhara. It could be e.g. “getting a glass of water from the kitchen”. I have not seen a PS for such daily activities.”
1. The post is about akusala-mula Paticca Samuppada, which starts with “avijjā paccayā saṅkhāra.”
– Getting a glass of water does not fall under that.
2. The Tipitaka reference that you provided explains what is involved under “avijjā paccayā saṅkhāra“: “Tattha katame avijjāpaccayā saṅkhārā? Puññābhisaṅkhāro, apuññābhisaṅkhāro, āneñjābhisaṅkhāro, kāyasaṅkhāro, vacīsaṅkhāro, cittasaṅkhāro” AND “Kāyasañcetanā kāyasaṅkhāro, vacīsañcetanā vacīsaṅkhāro, manosañcetanā cittasaṅkhāro. Ime vuccanti “avijjāpaccayā saṅkhārā”.
– Note that Puññābhisaṅkhāra, apuññābhisaṅkhāra, āneñjābhisaṅkhāra are generated via kāyasaṅkhāra, vacīsaṅkhāra, cittasaṅkhāra. But the second verse above explains that ONLY sañcetanā are counted under akusala-mula Paticca Samuppada.
– Here sañcetanā means those that involve “san” (lobha, dosa, moha).
– That is why “getting a glass of water from the kitchen” does not fall under this category.
You wrote: “What I do not understand: why is the word “kamma” not used in PS and where is it created?”
The answer is partly explained above. Not all kamma are bad. Kamma basically means “action.”
– Punna kamma (moral deeds) are done with punnabhi sankhara.
– Pāpa kamma (immoral deeds) are done with apunnabhi sankhara.
– Kusala kamma (in Kusala-mula Paticca Samuppada) are done with “kusala-mula paccya sankhara” instead of “avijja paccaya sankhara.” Those kamma help one attain Nibbana.
– Then there are abyakata kamma (kammically neutral) like in “getting a glass of water from the kitchen”.
You wrote: “..Lal explains in the post “Key Steps of Kammic Energy Accumulation” that kamma is created in the step “upādāna paccayā bhavo”. But is it also created in sankhara paccaya (kamma)vinnana and kammavinnana paccaya namarupa?
– This is exactly what I tried to explain in that recent post, “Key Steps of Kammic Energy Accumulation.”
– We don’t automatically start accumulating kamma with “avijja paccaya sankhara.”
– Kamma accumulation needs a trigger, as explained with the above post and the next post, “Generating Kammic Energy in the “Upādāna Paccayā Bhava” Step”
– That trigger is explained in #1 of that second post in detail. The time sequence is discussed in detail in #1 through #3 of that second post referred to above. Then time sequence moves to the “avijja paccaya sankhara” and goes through all the steps in akusala-mula PS.
– So, please read those two posts again carefully.
You asked: “Kamma is energy created via sankhara and stored in the mental plane, so it is namarupa? Kamma seems to be apart from citta, cetasika and rupa..”
Kammic energy is created in javana citta, not all citta.
– Such javana citta involve punnabhi sankhara, apunnabhi sankhara in akusala-mula PS. See above at the beginning of my response.
– As explained there kamma are various types. Only those kamma that involve “sancetana” (with greed, anger, ignorance OR “san“) contribute to akusala-mula PS.
Please feel free to ask questions. It is important to get these basic ideas right.