That was a while ago, but I remember that Zotero used to have a blue dot to indicate that there is an attachment of some sort. In current Zotero, you have something better.

Just right-click on the top row (where it says Title, Creator, Date, etc.), and make sure 'Attachments' is selected. Then, an icon showing the attachment file type will show. You can drag and move the Attachments icon anywhere you want.