Test Cases need to be archived before deleting them. This feature prevents accidental deletion of test cases and, hence, test cases can be deleted only after archiving them.
...
Archived test cases can be unarchived at any time to move them back to the active test case list. If not required anymore, the archived test cases can also be deleted.
Note: A maximum of 10 filters, including system as well as custom fields, can be selected at a time.
Impact of archiving test cases:
All the versions of the test case will be archived.
All existing folder associations will be lost.
The existing execution of the selected test cases will be preserved along with attachments.
Note: Users with Test Case “Edit” permissions can archive test cases.
Other Points:
If you export test cases With All Execution, all the test cases archived as well as unarchived will be exported.
In the Test Report configuration screen, the Archived Test Cases filter is provided. If you want to include the archived test cases in the report, then select the filter.
In Traceability Reports, the archived test cases are displayed with the Archived tag.
If a test case that was created through Automation is archived, then the import of the result file containing the same test case will create a new test case.
Import Test Cases: If the import is carried out by mapping the Key, then the archived test case key will not get mapped. The archived test cases will not get imported. Such test cases will be skipped during the import.
...