I finally succeeded at figuring out how to apply a Journal Entry to an Invoice via SuiteScript 2.1. I wasn't able to find anything about this anywhere and it is a really kind of strange and unexpected process with gotchas. I'd love to post my findings on netsuiteprofessionals.com but I noticed that my only option is to "Ask a Question". Is there a way for me to contribute, or is it not the right place for that?