[{customer:"QKD",parameter:"category_b",locations:[{city:"Tel Aviv",category_a:0,category_b:22.0,category_c:612.0,}]}]

db.collection.aggregate([{"$addFields":{"locations":{$map:{input:"$locations",as:"location",in:{"$mergeObjects":["$$location",{category:{$reduce:{input:{$filter:{input:{"$objectToArray":"$$location"},as:"obj",cond:{$eq:["$$obj.k","$parameter"]}}},initialValue:null,in:"$$this.v"}}}]}}}}}])