“May I ask about walking meditation techniques that Tipitaka approves or in line with?”
Meditation can and should be done in all four postures.
– The key here is to understand what is meant by “meditation” or “Bhavanā”
Bhavanā is to cultivate the Eightfold Noble Path. That can be done in various ways but is based on two things.
(i) One must understand the Dhamma (which involves learning/contemplation.) That cultivates Samma Ditthi.
(ii) Live one’s life accordingly (in particular pay attention to Samma Sankappa, Samma Vaca, Samma Kammanta, and Samma Ajiva.) Make effort in a sensible, consistent manner (Samma Vayama) and one will automatically get to Samma Samadhi. Samma Samadhi is not necessarily jhana, but that could happen too. That will definitely happen (getting to jhana) when one gets to the Anagami stage.
That needs to be done in all four postures and at all times.
It seems to me you (and most people) believe that Bhavanā requires one to sit down like a statue or to just walk up and down calmly (which could be called “formal meditation”). One can contemplate on Dhamma concepts in those two modes. That could be an essential part of the whole process.
– But Bhavanā is NOT limited to those two.
– One must be engaged at all times, making sure to avoid dasa akusala and to cultivate dasa kusala. That is complete Bhavanā or “following the path.”
Regarding Ven. Sona’s account: He got “burned up” mentally by making too much of an effort (probably by doing too much of “formal meditation”).
– That could be stressful to the mind.
Others just do “formal meditation” for an hour a day or go to a retreat once in several months, and assume that is enough. That is the other extreme.
One needs to stay away from both those extremes and be consistent.