Customers often need access to full support requests data for many reasons eg. reporting, syncing with internal project management tool etc.
Empower your customers using Requests Export for Jira Service Desk. Let them export/download requests to CSV/Excel from Customer Portal.
If you haven't installed, please install from Atlassian Marketplace here: https://marketplace.atlassian.com/apps/1222472
If you are customer, please ask the organization to install this app.
Once this app is installed in Service Desk, there will be new action under profile menu.
Click on Export my requests and it will open dialog where you can export all issues.
Here you can export to either CSV or Excel.