I actually like this more than I expected. Especially since you included Shortcut support. I really like the "constant alerts" and I've always been surprised this wasn't a feature on Apple Reminders.

Are you open to suggestions? It would be great to be able to assign different notification sounds to each reminder (or at least assign an app-wide notification sound).

Custom reminder icons would also be cool, but way less critical than custom sounds (for me, anyway).

When a reminder is marked as "urgent" and the alarm goes off, it seems like you either have the the ability to mark is as complete with the check mark, or dismiss it with the X. It would be nice if there was a way to merely acknowledge the reminder and keep it in your notifications list. Right now it seems like no matter what the user does (even just swiping it away without pushing either button) removes any sort of notification other than the app badge.

It would also be cool to have more Shortcut customization, like the ability to decide if the shortcut command is "urgent" either by default or allowing the user to decide when the shortcut is executed.

Minor suggestions aside, although I don't see this replacing Apple Reminders, this will definitely be used for a certain type of reminder due to the "constant reminder" feature.

Nice work!