Last week we rolled out a new feature to Jira Service Desk that adds the ability to download all attachments from an issue.
From the action menu in the top-right of a Jira Service Desk issue select "Download all attachments". This will download all attachments from comments and from the description into a ZIP file.
We are continuing to improve the attachment experience across Jira and will have further updates to share in the coming weeks and months. Thank you for your support and patience.