For what ever reason is appears WD didn’t include that option in the 2nd Gen v2.x single bay My Cloud units. There have been multiple requests in the Cloud Ideas subforum for WD to re-add the scheduled backups option similar to what the 1st gen single bay My Cloud unit has.
https://community.wd.com/t/schedule-queue-usb-backups/96993/
More requests here: https://community.wd.com/search?q=schedule%20backup%20category%3A107%20order%3Alatest
