I was digging through the Amnesia.exe file using
string2 (kudos to Combine for linking it to me) and I found some interesting bits. I was trying to figure out what caused Amnesia - Justine to block the save feature but couldn't find that one. But what I did find was pretty interesting.
These two can be used in your custom_story_settings.cfg file to specify the lang file a bit more:
ExtraLangFilePrefix = "extra_"
DefaultExtraLangFile = "english.lang"
So here you can change the name of your lang file. If you don't want it to be named extra_english.lang, you can easily change it now.
From what I've tested, it does not seem to work to set ExtraLangFilePrefix as empty.
What's even more interesting is that you can use slashes for directories.
ExtraLangFilePrefix = "config/lang_main/"
DefaultExtraLangFile = "english.lang"
This will set it up similarly to a full conversion mod - within this folder path.
I also found a script function by the looks of this:
void AddKeyPart(int alKeyPart);
But I'm not sure what it does.