Hi, Shameless self promotion, but I think it will be useful here… because it’s useful for me!
About 5months ago I created a screensaver for Raspberry Pi for people who use Kodi with the Pi & computer monitors (aka non CEC).
It disables/enables HDMI, which will send your computer monitor into standby/sleep. simple yet handy!
Download the latest version for here, and install from Zip