Ever done any UI programming or other paradigms where you have a specific OS thread used for cross runtime synchronization but you need to efficiently call back

Ever done any UI programming or other paradigms where you have a specific OS thread used for cross runtime synchronization but you need to efficiently call background threads knowing exactly what's running where? Async/await handles that well and so far the other paradigms just have not targeted these use cases well. Message passing and promise libraries end up looking a lot like async/await with less sugar. (Compared to C#'s async/await implementation. The level of sugar depends on the language, of course.)