I might be mistaken, but I don't think you need steam to run it. Many people run multiple overhaul mods concurrently (though separate saves, obviously), and to play each one, you can create a custom exe on your desktop. You can add the exe shortcut on your desktop and just don't edit any of the parameters. From Steam, click on the gear icon when viewing 7 Days in the Library. Click Properties (I think) and you should see an option to view the local files. That should open your steam directory
"[drive and folder you save your steam library]\Steam\steamapps\common\7 Days To Die"
In there you should see the exe file. Right click and select Send to Desktop. You'll want to close steam completely before you launch the exe from the desktop (right click the icon in the system tray and select Exit) just to make sure it works as intended. Again, I don't think steam needs to be running for it to work, but give that a go.