You can see the list of created Apps by navigating to the menu [App > App List] in the management console. The App List presents only the Apps that you are authorized to access as a logged-in user.
While the list indicates whether each app has been built or not, it also provides download links for the successfully-built apps. If you select an App and click the Copy button at the top right side of the console, App Builder will create a copy of the selected App with the name "[App_Name]_copy".
If you copy an App by clicking the Copy button, you cannot change the name of the created App.