I found a 2 years old post on the WP.org forums and I have exactly the same question.
Here it is:
I used scheduled pages to publish course modules/assignments as specific times for educational websites.
But when custom menus are used this seems impossible with the current feature set.
What I’d like to see is the option to put all of the scheduled pages into the custom menu but not have them a) show up in the navigation and b) be published until their scheduled time.
Has anyone found a way around this or have a similar problem?