For anyone having a similar problem to mine... If you open up the SE code you can find the exact characters Earendel used to name the elevator station, and copy/paste those into the diverter text box. Mostly. The rich text icon for the elevator is NOT the same as the one you can select in the menus, so you have to enter the right one manually.
[img=entity/se-space-elevator] Nauvis ↓
[img=entity/se-space-elevator] Nauvis ↑
Also notice that there should be 2 spaces before "Nauvis" and only 1 after (but the post formatting automatically removes the double space). Truly rage-inducing. Luckily, once you do this on one diverter you can just shift-click to copy it to the rest of them.