EnigmaGrey: The problem with this is, as we have many people whom are new to linux, if the file were hidden or tucked away, they may not be able to find it.
If you'd like, you can add the -cachedir=dir/to/cache/ variable (either added to the launch paremters via Steam or added to the jsno file) to change the directory.
I do not have an example off-hand of the json/sh file though, as the computer containing my linux partition recently kciked it. Let me know if you need it, though.
I hope you will reconsider. Just because someone isn't going to immediately know where the save files are doesn't mean they want them strewn around their home directory. The Documents directory has been completely ruined in Windows by poorly behaving third party software, I hope this won't become the norm in Linux too.
That said, adding -cachedir=$HOME/.config/zomboid fixes the problem. I have no idea what this Steam thing you mention is, but here is a copy of the only json file I could find:
$ cat ./data/noarch/game/projectzomboid/ProjectZomboid64.json
{
"mainClass": "zombie/gameStates/MainScreenState",
"classpath": [
".",
"jinput.jar",
"lwjgl.jar",
"lwjgl_util.jar",
"sqlite-jdbc-3.8.10.1.jar",
"uncommons-maths-1.2.3.jar"
],
"vmArgs": [
"-Xms1024m",
"-Xmx1024m",
"-Dzomboid.steam=0",
"-Dzomboid.znetlog=1",
"-Djava.library.path=linux64/:.",
"-XX:-UseSplitVerifier",
"-Djava.security.egd=file:/dev/urandom"
]
}