Database
[{"postId":ObjectId("62dffd0acb17483cf015375f"),"userId":ObjectId("62dff9584f5b702d61c81c3c"),"state":[{"id":ObjectId("62dffc49cb17483cf0153220"),"notes":"these are my custom notes!","lvl":3,},{"id":ObjectId("62dffc49cb17483cf0153221"),"notes":"hello again","lvl":0,},]},]
Query
db.collection.update({"postId":ObjectId("62dffd0acb17483cf015375f"),"userId":ObjectId("62dff9584f5b702d61c81c3c"),"state.id":{"$ne":ObjectId("62dffc49cb17483cf0153221")}},[{$set:{state:{$concatArrays:[{$ifNull:["$state",[]]},[{"id":ObjectId("62dffc49cb17483cf0153222"),"lvl":1}]]}}}],{"new":true,"upsert":true,})