Database
[{"_id":1,"title":"dummy title","assignments":[{"_id":1,"name":"a1","members":[{"_id":11,"full_name":"john doe","aga":18},{"_id":12,"full_name":"john doe2","aga":18}]}],"settings":[{"type":"light","status":"enabled"},{"type":"flare","status":"disabled"},{"type":"toolbar","status":"enabled"}]}]
Query
db.collection.aggregate([{$project:{_id:1,title:1,assignments:{$map:{input:"$assignments",in:{_id:"$$this._id",name:"$$this.name",memberIds:{$reduce:{input:"$$this.members",initialValue:[],in:{$concatArrays:["$$value",["$$this._id"]]}}}}}},active_settings:{$reduce:{input:"$settings",initialValue:[],in:{$cond:[{$eq:["$$this.status","enabled"]},{$concatArrays:["$$value",["$$this.type"]]},"$$value"]}}}}}])