Pinning Result Sets
Existing Result Set tabs are removed when you execute a script again. If you want to save a Result Set tab between executions, you can "pin" it using the Pin Tab right-click menu choice for the tab header, or by simply clicking on the tab icon. There is also a Pin All choice if you have multiple tabs you want to pin, and Unpin All to make them all be replaced at the next execution.
Whether Result Set tabs should be pinned by default can be controlled in the Tool Properties dialog, in the SQL Commander/Result Sets category under the General tab.