This onboarding project is a very promising initiative. I've felt for a long time that new users should be told the basics at the very outset and not just be left to sink or swim, very often leading to frustration for themselves and others.
What I would very much like this process to cover is how to use user space - the main user page and user subpages. There are plenty of new users who seem to think this is just like Facebook: once you've put your CV, self-publicity or advert on your user page, you've done it and that's your total involvement with Wikipedia. Or, the slightly more sophisticated ones create an unreferenced promotion page in their user sandbox, roughly formatted like an article; apply search engine indexing as VE makes it so easy to do; job done. Please include in the onboarding process guidance about what the user page is for and what it's not for; what to do when you've created a user draft and how to get it on the road to being accepted as an article; and intervene if they apply indexing in user space, which is almost never a valid action for a new user.