vorpX is actually supposed to rename the SteamVR desktop theater .exe automatically since SteamVR exists. It even checks every few seconds while running to not miss any potential changes at any time. When exiting vorpX the .exe name gets restored. One of the many little quality of life things vorpX does usually unnoticed.
If that doesn’t work for you, try to launch SteamVR before vorpX. That way vorpX can be sure where to find the desktop theater, without SteamVR running it has to guess. Usually that guess works well too, but it might not be 100% reliable under all imaginable circumstances.