So.... exploring some of TextEdit's new powers, I see a "complete" command in the edit menu. "Completely what," I wondered. The keyboard short-cut displayed by it is one I'd never seen before: "opt-(crooked, arrowed, power-on icon)"
I couldn't find it explained in TextEdit help; retreating to my Missing Manual I found that the process invoked is "word completion" and that the short-cut is "opt-esc."
I must be slow, never having noticed that ESC-key symbol before. I'm curious: when did Apple adopt that crooked, arrowed power-on as an escape symbol