Disabling all screen dimming when plugged in (AC)

[Spass]

> What I'd like to do is do from the command line what I do with the GUI
> by going to
> XFCE Settings-〉Power Manager -〉Display
> And reducing all values on the "plugged in" column to "never"
> basically disabling all power managent features (dimming, locking,
> sleep mode, etc) while the system is plugged into AC and not running
> on battery.

Hello, you can use "xfconf-query" commands for that. You would have to 
change the properties in "xfce4-power-manager" channel, mostly those 
with "-on-ac" in its name (like "blank-on-ac", "dpms-on-ac-sleep" and 
"dpms-on-ac-off"). Use this command to list those properties:
xfconf-query -c xfce4-power-manager -lv

So, to change an example property you would have to use this command:
xfconf-query -c xfce4-power-manager -p /xfce4-power-manager/blank-on-ac -s 0

Read more about Xfconf-query here: 
https://docs.xfce.org/xfce/xfconf/xfconf-query

Hope that helps.
Spass