Populate Custom Fields When Uploading Files
Where: This feature is available in Lightning communities accessed through Lightning Experience and Salesforce Classic, and is available in Essentials, Enterprise, Performance, Unlimited, and Developer editions.
How: This feature is available on files uploaded from Files home, from the Files or Notes and Attachments related lists, and the Lightning file upload component. File details can’t be added to files uploaded from feed posts or comments.
When uploading a file, users are alerted to required fields or validation errors that must be fixed before the file can be saved.