What I did:
What happened: Agenda continues to display the reminders in the order I created them.
What I expected: Agenda updates the reminders list to display them in the order that matches Reminders.app.
Things that might be helpful to know (Agenda version, OS and model, etc): Agenda 9.1.3, macOS 10.14.6
Alas, one of the many parts added to the new reminders app in 10.15 and iOS13 that haven’t been made available to third party developers, Apple simply doesn’t give us access to that information. Sigh.
Would you consider letting us reorder reminders within Agenda only? I benefit a great deal from organizing reminders into the order I want, then working down the list. As it is now, I pretty much have to ignore the all-day reminders in Agenda and switch to the task manager for ordering, which is unfortunate. I am a big fan of working with reminders through the Agenda interface.
I see how this could be useful, problem is that given that Apple doesn’t expose the API’s to read/write the order of reminders, I’m afraid that it would only lead to confusion why reordering reminders inside Agenda would not lead to them reordering in Reminders.
Perhaps not any more confusion than current reordering in Reminders not being reflected in Agenda 
I hope you’ll consider this at some point. I understand the limitations involved. I believe the utility of ordering reminders in Agenda would outweigh potential confusion of the order not being reflected in Reminders.
Sure, but that is a limitation we can’t get around, Apple just doesn’t make that available.