Add a new "Beanshell scripting host" to a blank workflow. Right click on it and do Configure.
Go to Ports. Add an input named fish, click the "Add input" button or press Enter. Nothing happens in the dialogue window, but in the workbench "fish" appears as a possible input to the processor. Resize the dialouge window or switch between "Script" and "Ports", and the new port will appear. Seems like some kind of redraw/invalidate problem, should be easy to fix.