Hi! I'm so sorry it took me so long to answer this, I was waiting until I could do a full thing with screenshots and everything, but life got super busy, so I'm just gonna give you the text explanation:
Basically, to make non-default, occult only eyes, you do it the same way you'd do the regular non-defaults, but make sure you clone the default eyes for the specific occult you're making the eyes for. So, when you open s4s, choose "add CAS part swatch" for creating your file. Do not choose "create CAS standalone"! Then, select just one of the swatches from the occult eyes (filter by eye color, and then by pack). Make sure under the warehouse tab you change the secondarydisplayindex number, and under the main tab you change the swatch color so that they do not conflict with defaults.
The occults that the eyes show up for will depend on which default eyes you clone; vampires will show up for vampires and spellcasters, mermaids for mermaids, aliens for aliens, and werewolves for werewolves.
Double check that in the studio tab, under categories, the correct occult boxes are checked, and then in the warehouse tab, that also lines up with which hide for occult boxes are checked!