Merge duplicate customer as Subcustomer through N/task

Solution

 let cusTask = task.create({
                    taskType: task.TaskType.ENTITY_DEDUPLICATION
                })
                cusTask.entityType = task.DedupeEntityType.CUSTOMER;
                cusTask.dedupeMode = task.DedupeMode.MAKE_MASTER_PARENT;
               
                    cusTask.masterSelectionMode = task.MasterSelectionMode.SELECT_BY_ID
                    cusTask.masterRecordId = '112255' //master record ID
                    cusTask.recordIds = ['2255','66332'] // internal ids of duplicates

                    Or to merge based on recent activity, use,
                    cusTask.masterSelectionMode = task.MasterSelectionMode.MOST_RECENT_ACTIVITY
                    cusTask.recordIds = ['112255','2255','66332']; // provide internal id of        all records. NetSuite will find most recent activity records automatically
                
                let taskId = cusTask.submit();