Hello, sorry for the delay, although i added a Single Player button for all mutation types, some of them are not meant to be played Single Player, there's to be expected some minimal bugs and sadly i can't fix them because the game's code doesn't allow me to apply an easy fix.
This bug happens when selecting any scavenge game modes on Single Player, the game loads the default list of campaigns to play, but when selecting the Cold Stream campaign there will be no available chapters due to Cold Stream scripts not supporting scavenge game modes.
The easy fix would be to remove Cold Stream from the list but it would remove it from other lists because it's the default list.
Another fix would be to edit the Cold Stream scripts to support scavenge game modes but i don't have the knowledge to do that because it involves map modding.
I hope it's no big deal for you or to any who encounters this bug, if i find a fix i will apply it, stay safe and have fun

If it's alright and with your permission, may I use some parts of this menu? I've been working on a menu for about 2 months now and I've had some pretty good ideas as for what to add. I mean if not it's okay, I'll just continue to make it for personal use. Been trying to find a splitscreen menu that offers everything from splitscreen mutations, cheat menu, and a few other fixes aside from the menu changes. Found an older splitscreen menu that offers splitscreen mutations but it hasn't been updated since the Cold Stream Campaign was added. I'll have to ask the other authors' permissions as well probably since I'd be using bits and pieces from other menus, assuming I can find a way to message them.

If you give credits, sure!
About the bug, seems like Cold Stream can be deleted from the scavenge list, someone did it in this mod, if you want to check it out
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2238957546