The idea is to control an RGB LED strip (or strips, though independent control of the various strips is not necessary) lighting my desk. I'd like to build 3 potentiometer sliders into my desk to allow me to change the color of the strip(s) on the fly. I should state that I am a complete newbie when it comes to electronic circuits, though I do have some rudimentary understanding. Basically, I'm looking for something like this https://www.superbrightleds.com/moreinfo/rgb-dimmer-switches/ldk-rgb3-three-color-rgb-led-dimmer/117/526/ but using sliders. Hopefully, I'd use the 12v DC power supply that came with the LED strip as the input to the device, then feed the 4 outputs to the strip. I would be grateful for any thoughts you may have and/or pointers to more information that may help me create this.
Figure 1. The RGB LED controller.
Potentiometers are designed to handle small signals at low currents. In the device you referenced the potentiometers are used to control a transistorised circuit which will handle the relatively high currents drawn by the LEDs. Dimming will be achieved using pulse-width modulation (PWM). This switches the LEDs on and off at a rate faster than the eye can detect and by varying the on-time pulse-width dimming can be achieved.
Figure 2. PWM signal transitioning from high pulse width (75%) to low (25%) and back again. Note amplitude remains constant. This will result in an apparent brightness of 75% and 25% of full brightness. Source: LEDnique.
The simplest solution to this will be to purchase the unit, open it, figure out what resistance value the potentiometers are, disconnect them and wire in sliders of the same resistance value having identified the pins on each.
Your biggest problem will be making a nice panel for the sliders.