As of July 22, 2024, Plus merchants can use apps with compatible UI extensions in draft order checkouts.
For an app to be compatible with draft order checkouts, the developer must update their app to the latest UI extension version. This allows the extension to react to draft order restrictions like un-editable cart lines or discounts.
Once the developer updates their app, it will automatically start running in draft order checkouts and regular checkouts.
Learn more about customizing checkout on this page