[{"_id":ObjectId("63a00087347cec20308de2ec"),"registration":{"email":"admin@admin.com","password":"password"},"profile":{"name":"My Name","mark":"r4u4tlbOSq","category":"general",/**other 60 fields*/}}]

db.collection.update({},[{$addFields:{"profile":{"$mergeObjects":["$$ROOT.profile",{"hello":"world"}]}}}],{upsert:true})