[{"example":{"key1":{"name":"test1"},"key2":{"name":"test2"}}}]

db.collection.update({},[{"$set":{"example":{"$arrayToObject":{"$map":{"input":{"$objectToArray":"$example"},"in":{"$cond":[{"$eq":["$$this.v.name","test1"]},{"$mergeObjects":["$$this",{"v":{"name":"new value"}}]},"$$this"]}}}}}}])