Database
[{"_id":{"$oid":"63e8af476a3674484ea14888"},"my_id":321123,"version":0,"parameters":[{"a":1},{"a":1,"b":2}]}]
Query
db.collection.update({"my_id":321123},[{"$set":{parameters:{"$concatArrays":["$parameters",[{"a":1,"b":2,"c":3}]]}}},{"$set":{version:{$cond:{if:{$and:[{$gt:[2,/** version*/0]},{$lt:[2,/** version*/{$size:"$parameters"}]}]},then:2,else:{$size:"$parameters"}}}},}],{upsert:true})