How to allow the same heroes to be picked in a Co-op Botgame?

Hi,

a friend and me wanted to pick the same heroes in a custom Botgame.

i tried to set up "GameRules:SetSameHeroSelectionEnabled(true)" in addon_game_mode.lua (there are multiple in Dota Folder but only one which contained this specific term so i thought this is the right one: game>dota_addons>cavern>scripts>vscripts)

Also tried to set the Value of each hero in Herolist.txt (there are multiple too, dont really know which one is the right) to -1.

Neither of them worked, can someone help me out how to do it? Or did i just catch the wrong files to do some changes?

Thanks in advance for you very much appreciated help :) Greetings, Hans