I was. Suggesting edits seems to be the way to get started.
So, I’ve known for a long time that “undo” in the vi editor can be accomplished by pressing escape, then the “u” key. But how to “redo” eluded me this morning. I tried various things before resorting to a Google search: escape, “U” (capital “u”); escape, “r”, etc. Turns out it’s the Control-R. Duh.