netris-nestri/build/steam/config.vdf

"InstallConfigStore"
{
        "Software"
        {
                "Valve"
                {
                        "Steam"
                        {
                                "CompatToolMapping"
                                {
                                        "0"
                                        {
                                                "name"          "proton_experimental"
                                                "config"                ""
                                                "priority"              "75"
                                        }
                                }
                        }
                }
        }
}