Using /name CMD straight after launching the game will only change the name for the config of the default mod - etmain if 2.60b or legacy if ETL. To actually change name or anything else for the config of the specific mod, you gotta switch to that mod first. You do that either by the main menu -> Mods and choosing the mod from there, or by simply connecting to a server using that specific mod, but I guess the first option is gonna be more useful here. If those are impossible to finish for some reason, there's always editing the .cfg files from the OS side