I have object A with a list of B.
I used @CollectionOfElements

and it created me a third table that maps between the 2.
Is it possible to tell it somehow to not create the third table, but just add some mapping column to the B table?

It is a wasted table as i see it...

If I understand your problem, I would use the annotation @ManyToOne relation.
This way, you are telling him that each elem B has only one parent A.

that way you will not have another table

correct.

tried that already
but then i have a different problem.
when i merge A (containing a list of B's), it returns me empty list of B's.

Thats why i wanted to try CollectionOfElements.