This is BURIED in the UI.
After you setup STHM (you wont see anything until you do)
tap on the SmartThings Home Monitor > Banner
(new screen) gear icon top right
(new screen) tap on the Security header
(new screen) tap on Set response
There you go… Record Video.
(…and for the record, my cams are Arlo Pros)
I mean - there’s some REALLY bad discoverability issues here. Bad enough to lead end users to believe:
No - they do, nobody can find it.