By default, when updating a record, existing data in the field are visible and can be edited. This feature allows you to prevent users from seeing existing data (cell values will be hidden and the field always starts empty) but at the same time, new values are still allowed to be added.

This option is available for some field types. Linked records, long text, & attachments. To find it go to

By enabling the Show existing values toggle, you can choose to display the existing files in the field while using the add-only mode. This option enables you to view the files that are already present, but it prevents you from deleting them.

Allowing employees to add new notes/comments to a record without being to able to edit the existing notes.