Hello! Since I am still trying to get more into the scripting side of the platform I tried to make the available documentation more accessible. Obviously the official documentation should be the first thing you check out, it can be found under “API Reference” in the Official Documentation. If you want to delve deeper than that and are not afraid of a bit of tinkering - this is the resource for you 
I started by generating a clickable documentation from the available lua annotations because those were the biggest chunk of scripting info I found so far. I did that with (LDoc), which worked after a bit of -as announced- tinkering.
I uploaded the generated docs to our company page for fast access:
https://www.gentleforge.com/yahaha-lua-api-generated-docs 
(At least) two remaining issues :
The annotations were not fully compatible with LDoc’s supported documentation syntax so I had to manipulate a few of them to be able to generate the docs. I am not really fluent in lua-syntax, so that might have caused errors. If anyone is more advanced with that and interested in checking/solving this message me :).
@KimMakesGames already gave me the hint that I should check out EmmyLua for info about the annotations - about to do that next.
Secondly, obviously the formatting/embeddedness of the whole documentation, which is something that I will try to work on as soon as I have more time.
I hope this helps you to build great things