Hi Sebastien
When you are sending the mapping to the input of a web service, you will make use of an Export Mapping. Make sure in this mapping you select the Value attribute from the Wrapper:
Then you will see it when you try to connect entities to it:
And you can use the “Map automatically...” button again to create the new attribute in the Domain Model.
Once you are past this, you will create the Mendix objects that will form the array in a Microflow that could look something like this: Model Share