Hello Svgeesus,
sorry I did not express this precisely enough:
It's no rocket science to shunt one leg and approach the target output voltage.
If you really want to use a trimmer (which I would avoid, see comment from TIN above), the next step is to replace one resistor by another resistor and a trimmer in series.
Regards
try
Added: excel screenshot
You calculate yourself a divider (R1 and R2 in series). Next thing is to shunt one leg of the divider by installing R3.
Depending on the intended precision you could place other bigger resistors R3', R3'' ... in parallel to R3.
You could as well extend R3 by putting another resistor R4 in series to R3, maybe another.
Countless variations are possible.
At some point you exchange comfort against stability by replacing any resistor (neither R1 nor R2) in your resistor by a smaller resistor and a trimmer in line to each other.
Look at the scheme from cellularmitosis:
Imagine R3 was 1k Ohm before. Now it has been replaced by 400 Ohm and a trimmer with 1 k Ohm.
Around trimmer mid point (500 Ohm) you roughly hit the 1k (~900)
Tighter version:
Make R3 910 Ohm (1k||10k) and use a trimmer rated 200 Ohm.