Code Review:

fun onRefreshTrackCollection() {
    val job = scope.launch {
        refreshTrackCollection()
    }
    when(job.isCompleted) {
        // show snackbar message
    }
}

How do I better execute a UI change when a coroutine job is complete?

I would have a StateFlow for isShowingSnackbar (or add it to a data class that holds UI state that is exposed via StateFlow), and have

if(isShowingSnackbar)

in my compose code.

I'll give that a go