What is Zombie History? Every time a Zombie is instructed to do something it is logged in the Zombie History for each individual zombie. Normally this is seen through a debugger, but I made a function to print it out in-game.
How Do I View Zombie History? You'll want to add this line somewhere in your scripts, even the map script is fine:
Here is the function I wrote that you'll need to copy and paste, I put it in _zombiemode_utility.gsc since almost every script includes it:
Then after, you'll want to toggle the DVAR "zombie_history_debug" to any number of history events you want to see. It'll print the most recent at the bottom, like the console.
How Can I Log My Own Events? Stock scripts already log events for you, but if you want to log your own you'd want to do something like:
Call it on a Zombie AI and the first and only parameter is a message (usually is the function name the log is in and some helpful description about what is happening).