Database
[{addition:[{key:"city",label:"CITY"},{key:"gender",label:"GENDER"}]}]
Query
db.collection.update({},[{$addFields:{data:[{key:"city",label:"CITY"},{key:"city2",label:"CITY"},],keys:"$addition.key"}},{$set:{data:{$filter:{input:"$data",as:"item",cond:{$not:{$in:["$$item.key","$keys"]}}}}}},{$set:{addition:{$concatArrays:["$addition","$data"]},data:"$$REMOVE",keys:"$$REMOVE"}}],{multi:true})