Studio Designer Parameter function or expression to capture User Name

I'm building a report in studio and have a need to create a parameter that will capture the User Name of who is running the report. I know I can do this IN the report using Page Info control box. But I need to capture it as a parameter so that I can use the parameter as means to filter a SQL dataset query.

I've done this many time using SSRS, but I can't seem to find a way to do this in OneStream Studio Designer. Any suggestions?