On deletion of folder inside the workspace , a trigger has to be fired so that all the details of files(filename,document number) present inside the folder should be copied into the csv file.
Please share the code for the same.
A trigger writing to a csv file is a bad idea. triggers on worksite tabels should be avoided at the best of time.
I would create a backup of the projects table, and add new folders to this on a regular basis to act as the backup. Worksite records folderdeletions in Change events as well as documents being removed from a folder, and you can configure the database to record Folder deletions in Document history. Checking for these change event and copying the relivent additional information to a cs as a asyncronos action would be my recomendation
Hope this helps