Issues
On this tab you will see the list of issues, along with their priority, type, Key, summary, assignee names, and status.
You can take quick actions like, Edit release, Archive release, or mark the release as released. You can also copy the link of the given release and share it with others. + Add issues option is to quickly add new issues to the release, instead of going all the way back to releases in Jira.
Columns
On the issue tab can be configured as needed. You can select all the Jira default and Jira custom fields as columns.
Group by
This dropdown allows you to group issues by Jira default and custom fields. This gives you complete flexibility over deciding your focus on issues in the release. This enables you to do better planning of the releases because of proper segmented view.
Expand All or Colapse all allows you to view/hide issues in different groups.