You use this dialog when you want to resolve an issue and want to mark the issue as a duplicate of an existing issue. When you select Resolved as the issue's Status and select Duplicate as the Resolution, the IDE displays a text field for the id of the issue that is duplicated. You open this dialog box by clicking the Search button (...) next to the of Issue text field in an issue's form.
To specify the issue that is duplicated, enter the id or text contained in the summary of the duplicated issue.