It occurred to me while responding to https://github.com/tc39/proposal-pattern-matching/issues/322 that we could potentially simplify a pattern like Number and let x as Number x, i.e., treat Pattern identifer as Pattern and let identifier. You still need let for cases where you don't need some other pattern, but it would cut down on repetition in other places:

match (command) {
  [("up" or "down" or "left" or "right") and let direction, Number and let steps]: handleMove(direction, steps);
  ["jump", Number and let howHigh]: jump(howHigh);
}

Could be simplified to

match (command) {
  [("up" or "down" or "left" or "right") direction, Number steps]: handleMove(direction, steps);
  ["jump", Number howHigh]: jump(howHigh);
}

Though if we did want to support that, I'd almost want it to be a follow on so the community would have time to understand how let/const patterns work first.