View Single Post
Edit > Undo is available. I didn't realize this when I opened this thread because OmniFocus Undo does one character at a time.

When I realized I'd wiped out the action description, I instantly typed Command-Z, expecting all of my typing to be undone. I didn't notice at the time that I'd actually untyped one character and could have retrieved my action description if I'd typed Command-Z more times.