I created a custom field in the NetSuite GUI and entered a few translation labels/strings in 2 or 3 languages. I then imported that field as an SDF object into my IDE. I would have thought the translation strings would be included in the XML definition of the field but apparently not. I deployed that field to another account and obviously there are no translations there. I discovered "translation collections" but I'm not sure if they are related to my problem.

They are indeed. You need to reference translation strings from a translation collection which you’ve created (either from ui or through sdf). Sdf doesn’t track translation strings entered directly onto custom objects

Thanks @SimonC, I'll look into it.