How to update a 4x nested array Object of a collection

I am trying to figure out how I would update an object I have that is inside of a nested array in one my collections.

Here is a picture of how the data is structured.

How can I replace the last object on the list “>4: Object” using a Collections.Update method on the server?

What all information would need to be passed to the server method to be able to locate the object? Also the object does have a unique _id: