Reminders don't pop up, they are just in a list somewhere and you have to open up the list but there's no actual pop up or sound if you set up a reminder for a specific time. It's better to use the alarm feature for reminders. My phone has too many notification in the notification shader and you would need to take a look in each notification. It would be better to have an alarm feature or allow users to make a priority notification on phone or a pop up or open the app automatically when a reminder is due with alarm sound or sound notification..