For the Android app:

When adding reminders to a calendar event, the current experience takes the user through a lot of clicks. This should be streamlined.

I propose that the click to add a reminder or change a reminder opens a popup with preset choises that the user can control in settings. The user should at this stage have the opportunity to single press an option, making the pop-up close immediately, and leaving you with the exact same view of the calendar event setting as before. Of course there should be an option to add a costum reminder, which should change the view in the pop-up window to a scrollable timer of with the choice of weeks, days, hours, and minutes in front of the scrolling feature, which should replace the current system of tapping the field, then entering a number. This method of scrolling versus entering a number could also be left up to the user in settings.

Inspiration can be drawn from the Samsung Calendar app.

Best regards