Are you sure? Under File drop down? Odd that it would be missing, it's in mine. Have you tried to verify local files via Steam? Sorry, I wish I could offer more. I'm sure someone will be along to offer more. Good luck!
Desktop: i7 4770@3.4Ghz (passmark 9809), 12GB RAM, Win 10/64, GeForce GTX 1080 (passmark 12006), 1TB SSD, 1TB HDD; Laptop: i7 4800MQ@2.7Ghz, 16GB RAM, Win 10/64, GeForce GTX870M , 1TB SSD.