This is a customized dimmer for a SmartGlass (switchable privacy film) installation that fits into a standard electrical box as a decora style insert.  The insert houses a 6mm slotted potentiometer (WL branded) and an optional 5mm LED.

In action:

It's unlikely you want exactly this.  I included the Fusion 360 file for you to customize, and I have posted a blank Decora Insert model which may be a better starting point for you:

https://www.printables.com/model/1198667-decora-blank-insert-fusion-360-file

The potentiometer knob is separately posted here:

https://www.printables.com/model/1198622-potentiometer-knob-6mm-slotted

The model comes with an LED insert that provides a point source of light to diffuse under the white plate.  Print the LED insert with black filament.  The recess for the potentiometer includes a 1 layer bridge in the design so supports are not needed .. though it still prints a little better with supports.