As we don't have your design time configuration details, I will try to answer your question with the help of OOTB navigation rule pyCaseManagerLinks.
If you check the configuration for "My Cases" sub-menu, 2 Run Script action sets has been defined on it. On the first run script action set, "pega.desktop.showHarness" function is being called, which will show the harness in the workarea. This function takes an input parameter named "replaceCurrent". If you set this parameter to true, the harness will be replaced on each interaction.
Hope this will help you to achieve your requirement.