lynnelovestorun wrote: … But why did the update HIDE this when you go to Export the first time in Photos after this upgrade?
It's extremely rare for that to happen-- I don't ever remember my Export dialog starting out hiding like that for any upgrade, and we've seen it only a time or two here. I can't even imagine why anyone would close that section, really-- what would be the big advantage? In any case, you now know that this section opens and closes, so it'll never cause you a problem, again.
And since I've hijacked this post to rant, here's another hidden arrow

to watch out for-- the little ⌄ arrow with "Photos" doesn't show until you hover over it with the cursor. It can close that section so you can't even find Library or Favorites. There's one at Collections, too, as well as the other sections, but I wasn't hovering there, so the arrows are invisible. Now THAT's hidden!