I agree that the way the docs are structure are a bit idiosyncratic - Personally I am solving it with having a bookmark folder with all the bits I saved for later. Finding stuff 3 links deep is not easy otherwise. For a project with this little resources its quite quite good really. Stuff is documented even if you cannot find it right away :).
Most important are probably these 3 links for me:
https://www.espruino.com/ide/# the IDE allows you to both test stuff really quick and more crucially explore whats on the watch currently. You can explore and download these apps and modify them directly.
https://github.com/espruino/BangleApps contains all the apps source code in the apps directory. Look at how others did stuff.
https://www.espruino.com/Reference#software I use the API reference a lot. ctrl-f is your friend here.