Thanks - I actually didnt know how this was called.
I managed to get this to work in regular JS in similar use cases, but I really dont know the syntax for MongoDB to make this work & it seems to me more about how MongoDB handles nested object calls (eg. dot notation to access nested fields extraFields.topic1)
@steevej To use $push I need right now to go directly to the array email, so I need to somehow combine the dot notation of MongoDB with computed field names - something like "extraFields.topic1[stringExample]". Do you know how?
Edit: Maybe theres a better way altogether to structure this object and I am missing it.