There's no way to change the direction of the split-screen in settings for local co-op.

[Johnnyb]

I prefer split-screen to be vertical since it's you can see stuff a bit easier and I'm willing to give up some peripheral vision to see easier. Unfortunately that isn't an option in settings yet does anyone know if there is a command for this? Otherwise I'd really appreciate it if this setting was made available in a future update.

[nian]

Open console (F10 by default), type ss_splitmode 2 and press enter. Splitscreen is now vertical.

[nian]

Alternatively, if you want both players to be in fullscreen and swap views by pressing a key you can read my post here:
https://steamcommunity.com/app/1255980/discussions/0/3815158655066530434/#c3815158655066671311

[Johnnyb]

Originally posted by nian:

Alternatively, if you want both players to be in fullscreen and swap views by pressing a key you can read my post here:
https://steamcommunity.com/app/1255980/discussions/0/3815158655066530434/#c3815158655066671311

Dude that is ingenious I didn't know you could even do that. Also for me to open dev the console ( ` ) is default for me in source games. That's the tilda key and it's beside 1 and above the Tab button. I've never heard of F10 being the dev console key before.