Firebase integration add documents vs set documents

[xDelfino]

Hi everyone,
I hope I'm in the right group; I searched unsuccessfully for a solution to add documents via Configure Firestore data entity, document id is not possible to assign, in the google firebase firestore documentation it says to use set and not add to assign a non-automatic id but for example userId, can someone help me understand if it's a limitation or if I can't find the solution? forgive my bad English

I can update or create all the other fields but not document

[xDelfino]

Hi,
if no one can help me, can anyone of you suggest me how to do with Firebase Authentication create Firestore documents that have the Authentication UID as id? another way to develop this? thanks in advance