Annotating a Module is not saved persistently

Hello

I wrote a NodeAnnotation to add it to a module, because I want to find the node that this reference points to easily within the whole module, without always searching for it.

(Dont mind the name ; the "module" in the code below has nothing to do with the concept of module in MPS )

Adding and using this NodeAnnotation on a module of a solution works fine, just it is not saved when I close the project and open it again. Is that wanted behavior? If the answer is yes, can someone point me to the place where this is implemented, so that I can make a decision to either make a change in the code, or find another solution.

Greetings

Jochen