Found a bug: If you create an option set, and then look for that Option set name in the “Type of Choices” drop down, it doesn’t show up. At least it didn’t for me with my very first time using option sets.
The Fix: You have to reload the Editor’s browser tab. Then it shows up in the dropdown.
Took me a good 10 minutes of searching forums and youtube before I tried the “CTRL-ALT-DEL” last and final option.
P.S. That fact that I assumed it would just work (but didn’t without a refresh) says a lot about the quality of your Dev team and code. Namely, bugs like this one are so incredibly rare in my two weeks using Bubble thus far, that I would never have thought it would be something primitive like a page refresh to fix it.