I wish to alter the XP modifier from the new multiplier in v5.7 back to the old one. I also want to try a game setting to 1 (It is 0.7 in the original vanilla game) Where do I find the multiplier and how can I manually change it?
With Co8 5.7 as the active module, navigate to your ToEE/data/rules directory and locate the file combat_vars.mes. If you just want to revert to vanilla, delete or rename the file. If you want to adjust the percentage, open the file and change the appropriate figure. (There's only one line with an obvious figure to change.) If you're doing this for your own testing purposes or because you disgaree with the percentage, that's fine, but you're not helping us to verify a suitable percentage by playing with a different one.
The change to .6 hasn't made much of a difference in my game. If you want more xp you can do some random nightime stuff.