You could add the Delete file server behgavior to the Delete record page created by DataAssist, or on the update record page created by DataAssist.
You could also create a separate page that lists out all of the Files that are in the database and give a delete file button.
In either case, the way to make it work will be to crate a form with a hidden form element, and a submit button.
The init value of the hidden form element will be the ID for the product table.
You then create a recordset that filters the product table on the hidden form element.
When you apply the delete file server behavior, set the trigger to the Record set not being empty. For the file name, click the lightning bolt and select the File name column from the recordset you created.