duplicating testcases from Testplan view
It is evident from the current functionality and documentation that Duplication of Testcases from TestPlan section is not possible.
Copying test artifacts
http://www-01.ibm.com/support/knowledgecenter/SSYMRC_5.0.2/com.ibm.rational.test.qm.doc/topics/c_copy_overview.html?lang=en
But can I know if there any specific reason this option is unavailable, or an RFE is already open in this regard.
One answer
There is an existing RFE - Enable new test cases to be created in the Test Cases section of test plan via duplication (70610). However, we do have the equivalent capability in the test cases list view. Using "Filter by Test Plans" (the left hand side filter panel) can get you the test cases of the test plan(s) that you can duplicate.