You can work with types of entities: persistent and non-persistent.
Using persistent entities is simple and completely supported by Studio. If I understand your problem correctly, you can add a status field to your persistent entity and initially set it to “To be approved” value. Then in a separate screen load the same entities filtering them by this field and allow users to “approve/reject” them.
With non-persistent entities, you can display and edit data in memory and transform them to persistent when needed. You see an example in the Timesheets sample application. Look at WeeklyReportEntry entity and its usage in ApproveScreen.