As far as i can tell the handbook for VS is still not finished. Marvel wanted to start a german version first, but it seems that there are several parts not finished or english (copied from the wiki).
I helped out several weeks ago but its far from finished what i can tell and my time schedule doesnt allow continuous support for the handbook itself.
Of course it would help when a lot more (video) tutorials will be produced in the next time to teach new users how the engine works and also spread the word to the social media platforms. As for now im still waiting to get the 4.3/5 version in my hands because of the big interface change and then blow out a handbook with some help instructions and an own web tutorial series on youtube.
I guess for the editor itself it depends on what they still need to get the product finished and polished for the final release...
Maybe some icons? Maybe a professional splashscreen? Maybe other artwork for the software... (I can't think of other stuff which would help to actively support the dev team)
As for advertising i think its very usefull to show own produced games or post devlogs on other web portals like indiedb or other forums to let the people know how the game was/is made and link to the Visionaire Studio engine of course. People who like the game and have a creative streak will likely want to create an own game and click on a link to the engine.
kind regards
Sebastian