To get more than one cfg work at once:
put a . (dot) between and at the end of your codes.
(i will use these 2 as an example.)
"default_splitscreen"."default_mp_gamesettings".
The dot in between the splitscreen and mp_gamesettings needs to be a 00. So change the hex value of the period right after "default_splitscreen" to a 00 on the hex side. Now the period after "default_mp_gamesettings" needs to be a 0A. So the first period in the code above needs to be a 00 and the second (or last one) needs to be a 0A. I feel I maybe made this a bit confusing but people will know what to do

you also need a hex editor.