A .launch
file is just the storage of a Launch Configuration, it's not really meant to be looked at or manipulated directly by users. Instead, you look for and edit Launch Configurations via the dedicated dialog, invoked by the Run menu or the toolbar buttons (Run configurations and Debug configurations both reflect launch configs, but one launches the JVM in debug mode).
If you want to duplicate an existing launch, use the Debug Configurations or Run Configurations menu item to open the dialog and there you can select and copy one.