If y’all are interested in learning by example, the 1Writer action directory is a good place to start. See Adapting 1Writer actions - source for JavaScript recipes
I’ve adapted four of the scripts so far to Drafts and it’s generally pretty easy - you just need to work out the differences between the app-provided objects, but quite a lot of the code is easily reused. And even if not, it’s helpful to look at how others have solved a ton of text manipulation tasks.