Apply Order Discounts from the Backoffice in Umbraco Commerce v15

Hi, I’m working on a custom functionality in the Umbraco 15 backoffice using Umbraco Commerce. The goal is to enable editing of an order directly from the backoffice.

Specifically, I want to provide two options for applying discounts:

  1. A textbox to manually enter a direct discount amount.
  2. A dropdown to select and apply one of the existing discount codes.

Could someone please guide me on how to implement these features within the backoffice order editing interface?