That only works while you remain in the Clock app. It does not permanently change the settings on your Notifications Bar Clock!
I've permanently changed my notifications bar clock so that it always shows seconds. I need to show seconds on the notifications bar while I'm in my Interactive Brokers trading app because I'm trading 5 minute candles and I need to know exactly where I am in a 5 minute bar while in a short term trade. The Clock App is of no use for that.
How did you get it to display seconds in the notification bar clock?
I can't figure out how to do it.