“But what is the difference between the two or better asked how can sanna work without manasikara?”
As you said, Tobias, both sanna and manasikara cetasika are in ALL citta.
– They help each other. More precisely, sanna cannot identify an object without manasikara cetasika “pulling in” memories from the past.
When the word “parrot” is heard, the manasikara cetasika pulls in memories with that word. Then the sanna cetasika identifies that and a picture of a parrot comes to the mind.
– Of course, the cetana cetasika is responsible for “pulling it all together” with one’s gati and generating vedana, vinnana, etc.
– We also need to realize that sanna is more than just “identification.” The perception as a “good or bad thing” is also included in sanna. For example, an average human, upon seeing a beautiful object automatically generates a “sukha sanna” or a “nicca sanna.”
Also, see, “The Amazing Mind – Critical Role of Nāmagotta (Memories).”
So, it is a bit complex, but we need to contemplate those subtle aspects. You are on the right track. That is vipassana meditation.