Restoring Accidentally Deleted Submission Boxes
Submission Boxes that have been accidentally deleted can be found in the "Trash" section of the Admin Console.
Steps
【Step 1】 Log in to the Admin Console.
【Step 2】 Select "Subjects".
【Step 3】 Choose the relevant class and then Task.
https://gyazo.com/e47edb385ad8ec28ce2efc7b39d6af7c
【Step 4】 Click on the folder with the subject name.
【Step 5】 Click on the Trash tab.
【Step 6】 Check the box for the submission box you want to restore and select Restore.
【Step 7】 A confirmation screen will appear; select Confirm.
https://gyazo.com/d4240464d3a4ed184e9dc1821403560c
Reference
【Materials】How to Restore Accidentally Deleted Data in the Material Box
How to Restore A User Accidentally Deleted
You cannot restore the deleted Cards