replacing a 2k resistor with a 1k and trimmer - wiring
A trimmer or potentiometer is like two resistors. If there are two different voltages on 1 and 3 any voltage between can be reached by twisting the knob. This is why there are three terminals.

However, you only want one resistor, so just use pins 1 and 2 (or 2 and 3) and you neededn't wire pin 3, that would be like connecting a resistor to ground.


Source: https://www.electronics-tutorials.ws/resistor/potentiometer.html