One thing I've always wanted in a tool like this is the ability to map out probabilities, i.e., we do A, then B but after that we do either C,D or E. Each one on these has an associated probability (C: 0.4, D: 0.5, E: 0.1) and an associated estimate (C: 10 +- 5 normal, D: 12 +- 3 uniform, E: 3 +-1 normal).

The UI would look like a graph and like ms project it could include resource levelling in order to show bottlenecks.

I know this probably sounds complicated but I think it maps to reality fairly well and thus actually simple (fighting reality is hard).

I've been struggling with wrapping my head around asynchronous programming with callbacks, promises and async/await in JS, however I think it's finally clicking after watching these YouTube videos and creating a document where I explain these concepts as if I'm teaching them to someone else:

* Philip Roberts's What the heck is the event loop anyway? - https://www.youtube.com/watch?v=8aGhZQkoFbQ

* The Story of Asynchronous JavaScript - https://www.youtube.com/watch?v=rivBfgaEyWQ

* JavaScript Callbacks, Promises, and Async / Await Explained - https://www.youtube.com/watch?v=JRNToFh3hxU

* Async Javascript Tutorial For Beginners (Callbacks, Promises, Async Await). - https://www.youtube.com/watch?v=_8gHHBlbziw

* Jake Archibald: In The Loop - setTimeout, micro tasks, requestAnimationFrame, requestIdleCallback, - https://www.youtube.com/watch?v=cCOL7MC4Pl0

Edit... I've been rewatching these videos, reading the MDN docs, the Eloquent JavaScript book, javascript.info, blogs about the subject, etc. This further proves you shouldn't limit yourself to a single resource, and instead fill up the laguna with water from different sources if you will.