I left CDAP (SDK) running on my laptop overnight.
The computer most likely fell asleep and was woken up this morning. (As I use an external monitor and I turn that off overnight, I can't be certain.)
In one tab, I had Studio running (http://localhost:9999/ns/default/hydrator/studio), and I successfully saved my current pipeline.
I had another tab open in Chrome showing the Hydrator pipeline view (http://localhost:9999/ns/default/hydrator). It had switched to the CDAP homepage (http://localhost:9999/ns/default) overnight, so I switched it back to Hydrator using the menu in the upper left of the page.
My recently-saved draft did not show up in the list. I had to refresh the page to get the new draft to appear in the list. Otherwise, this method (saving a draft, going to that page) shows the list correctly. Something appears to be stale and cached that should not be.