Hello @Healthier31173772z5lm, you can duplicate your current design by clicking the "View All Pages" button in the secondary bar at top right (under the "Download" button, the one with the "1" in a square button) and there you can duplicate, create a new page etc. Happy designing!
If you are talking about the ability to duplicate a post within the Scheduler, unfortunately that feature didn't make it into the new Adobe Express. The Uservoice has a topic for the feature to be returned, it does say it is planned but adding your support is always welcome: