Is there a way to get a single record and use the outputs to update a specific item in a collection of records data variable?

I have a nested array of text items in firebase and I would like to make a function which shows the increase in the count of the items in the nested array without having to get the entire record collection every time. Can a get record request be used in the set data variable for a collection of records to pick the item matching the id and update the count of a nested array?