I am not even sure this is the right description, but in postprocessing under results>Design Parameter, you can change the active display design parameter. It says something like Parameter 1, 2, Maximum. It would be awesome to be able to pass the parameter number, and it changes the active parameter display, passing 0 could display Maximum.
Thank you for posting this idea. I think this lies at the heart of a deeper idea which should also display /allow selection of the parameter block in the Structure Diagrams>Design Results sheet. The OPenSTAAD function SetDesignResults() then is extended to support this capability. It will be added to the backlog.