Can a queue message in Azure Service Bus that has been set with ScheduledEnqueueTimeUtc be modified or deleted before its enqueued datetime?
In some cases I need to change or delete a message submitted for future delivery.
No, you can't. But you can cancel a scheduled message if you use a dedicated API added recently. Here's a post about it https://blogs.msdn.microsoft.com/servicebus/2016/07/11/cross-post-canceling-scheduled-messages/