MacularDegenerate

// listsToClear: defines the iOS reminders list(s) from which completed reminders will be removed. Additional lists can be added to this this array if you wish.
let listsToClear = ["Completed Archive"]

for ( j = 0; j < listsToClear.length; j++ ) {
  let reminderList = listsToClear[j]
  let cal = await Calendar.forRemindersByTitle( reminderList )
  let reminders = await Reminder.all( [cal] )
  
  for( var i = 0; i < reminders.length; i++ ) {
    let reminder = reminders[i]

MacularDegenerate

// days: specifies the number of days that a reminder will remain marked as complete before it is moved to the "Completed Archive" list.
let days = 7
let today = new Date()
let arch = await Calendar.forRemindersByTitle("Completed Archive")
let listsToClear = await Calendar.forReminders()

for ( var j = 0; j < listsToClear.length; j++ ) {
  let cal = listsToClear[j]
  let reminders = await Reminder.allCompleted( [cal] )