I am creating some custom WordPress code and using my current favorite bundler, Parcel. I decide this time to take a hint from the source code of TwentyTwentyOne theme and use chokidar-cli to write my watch scripts directly. Watch has always been flakely for me, but so far this seems to be working out well. Reminder that you find good things by reading good source code.
BTW Why Parcel? Simple: For most of the work I do nearly zero configuration required. Of course Webpack and Rollup are useful and more flexible, but I find that I seldom benefit from the time spent on configuration. Simple works for me most of the time.