How to dim & turn off external display when the main display is dimmed/turned off by the power saving options?

As the title says. My usual set up is a laptop (Kubuntu 20.04) connected to a fairly recent external display.

I found how to add a script in the notification to turnoff the external display when I lock the screen, but I cannot find an equivalent option or notification when the screen is dimmed or turned off by the power saving behavior. Is there such a thing?