Thanks Jeremy, but I continue to do something wrong.
I exported 555 photos (originals from Photo) to a folder on my desktop, and import them into the browser of FCPX. I have tried selecting them all and changing duration in the menu above and with ctrl D using of your method of “1.”, then adding them to a new timeline. Nothing happens, there seems to be intermittent background rendering, but not much.
Then I try taking these same photos and place them in a new timeline, select them all there and try again to change duration, but nothing happens again.
I’m sure it’s something small and stupid, but it’s a real roadblock for me.