● Using a cvars.txt File
You can create a file called "cvars.txt" and place it in the following directory:
C:\Program Files (x86)\Steam\SteamApps\common\left 4 dead 2\left4dead2\ems\admin system

This file will automatically execute all Cvars upon loading each map. Keep in mind each Cvar will need to be on its own line within the file.

Here's an example of how you can enter the Cvars:

god "1"
"sv_infinite_ammo" "1"
sv_gravity 200
scripted_user_func give,all,rifle_m60
scripted_user_func max_health,all,300

And here all the commands:

https://developer.valvesoftware.com/wiki/List_of_L4D2_Cvars

Thank you. :)