Anyway, it does not really answer my question : when I draw a new pitch bend curve over an existing one, both are “melting” together. Instead of the previous one being simply replaced by the new one, as this is the case in “automation”.
Additionally, if I want to fine tune a pitch curve without grid constraints, as you suggests, I have to carefully edit each of dozens (hundreds) of key points, which is unmanageable.
Why not changing the way pitchbend is edited, using similar curves than the ones found in Automation ? There, a fistful of key points are enough to create a smooth curve, as in my example with volume automation…