No "official" videos yet, but I heard they are coming.
The trick is
to click on the ends of the Stair Boundary line -- took me a couple of tries to figure this out
MacBook Pro Apple M2 Max, 96 GB of RAM
AC27 US (5003) on Mac OS Ventura 13.6.2
Started on AC4.0 in 91/92/93; full-time user since AC8.1 in 2004