I'm running kde 5.9.2 on Arch Linux. I prefer playing music over hdmi through external monitor from the laptop.
But after 10 minutes or so the power managment kicks in and turns off displays including the external monitor. So, there's music playing but no sound.

To avoid this I can change the display off time to a longer duration but it needs to be reset everytime the monitor is disconnected or use a dedicated music activity but both these workarounds requires actively changing the configs everytime I want to play music.

I'm not averse to running or writing scripts. So, is there a way to change/edit the power profile when an external monitor is connected and reset it whenever the monitor is disconnected ?