picking session now started from the UI, meaning the generated command n...

@helgemathee : the Reroute port command used to start a picking session if called without target arguments. This meant users could not learn how to call the function by using the UI and copying the generated command. (this is how all other commands in Softimage work). By moving the picking session to the UI, users can use the GUI to generate a command that they can then use directly in their own scripts.