wait_started_ms_ticks is set in SOS_Task::PreWait(), i.e. just before actually suspending, and again cleared in SOS_Task::PostWait(). For more about the choreography of suspending, see here.
wait_resumed_ms_ticks is set in SOS_Scheduler::PrepareWorkerForResume(), itself called by the mysteriously named but highly popular SOS_Scheduler::ResumeNoCuzz().
start_quantum is set for the Resuming and InstantResuming case within SOS_Scheduler::TaskTransition(), called by SOS_Scheduler::Switch() as the worker is woken up after a wait.
Ewald intends this post as an extension of the official documentation, so it’s best to read that documentation in conjunction with this post.