All the versions of the test case should be archived to delete that particular test case.
You can not carry out further operations like adding attachments, linking test cases, issues, and release - cycles on an archived test asset.
A. Archiving from Test Case detail page
B. Archiving from Test Case module list view
A. Archiving from Test Case detail page
Open the test case details page by clicking on the test case.
Click on the Archive icon on the top right corner of the page.
It will archive all the underlying versions of the test case.
B. Archiving from Test Case module list view
Open test cases module.
The test case list view opens with list of existing test cases within the project/folder.
Click on the Cog icon for the test case you want to archive and select Archive. The test case is archived after confirmation.
To unarchive an archived test case, click on the Unarchive icon at the top right corner.
Read Archiving a Specific Test Case Version