[KamiNuvini]

Please ignore

[maks]

server.cfg

sm_cvar mp_gamemode "coop"
sv_gametypes "coop"
sv_allow_lobby_connect_only "0"
sm_cvar sv_force_unreserved 1
sm_cvar sv_removehumanlimit 1
sm_cvar sv_maxplayers 20
sm_cvar sv_visiblemaxplayers 20

[V1SoR]

I think he wants to actually allow more than 4 players into the game. Downtown/toolz do provide some ways of simplifying the task, but none of them are meant for this.

Since the survivor_limit cvar in L4D2 is hardcoded at values equal to or lower than 4, you need to look for some multicoop/multiversus plugins. Or, what would I do is patch the binary realtime to remove the limit check. Although that is far from trivial.