If a device has Context Parameters you can access it from within the device edit screen.
HTTP(S) Stress Test
If an HTTP(S) device has Context Parameters you can find the list at the device edit screen on the Task tab. To open the Context Parameters manager, on the Tasks Configuration sidebar, click the bar action menu , and then select Manage Context Parameters.
Web Application Stress Test
For the Web Application Test, you can view a list of Context Parameters in EveryStep Web Recorder. Open the script for editing from within the device edit screen (the Edit Script button) and on the script editing pan, go to the Context Parameters tab.