We’ve added theme tracking for files on the files page in admin (Content > Files). This further solidifies the files section as a source of truth for all your files across your store.
Now, when you want to determine where a file is used, you can navigate to the files section in admin and see where a particular file is being used. This is especially useful to determine which theme is referencing which specific file.
Learn more about managing files in the Shopify Help Center.