Actually “my trips” works while in travel on an itinerary. It shows blue boxes you tap to get the various BPs. You can get the earlier BP as well (ie after it disappears from home screen during boarding).

I had to make multiple changes this weekend due to ORD snow delays and the app gets very high marks. I was able to rebook, change seats etc.

One improvement needed - on the layover cards in “trip details” it assumes prior flight came in on time so the connection time info is erroneous. Needs to be a live card that adjusts with the flow.