Following assignment submissions, instructors can upload multiple feedback files to students all at once.
Start at the 'View all Submission' grading screen of an assignment:
1) Download all Submissions (option on upper left menu)
2) Save Zipped folder to a local folder (desktop or other)
3) Extract folder, and you will see subfolders for each student. The subfolders contain student submissions.
4) Open the submissions, make desired feedback, and Save.
5) Once changes are completed, select all subfolders and zip. (If files were downloaded into subfolders or all files (if files were downloaded directly) and zip. (Note, do not zip the folder in which the files or subfolders are saved [as was done in the previous version of Moodle], but zip all the separate files/folders.))
6) Give the newly zipped folder a name.
7) Then upload that newly named folder in the Upload Multiple Feedback Files area.