Battery percentage

https://www.howtogeek.com/707865/how-to-add-complications-to-your-watch-face-on-apple-watch/

M1 Mac mini, macOS 13.1; Watch, series 7 GPS/cellular, watchOS 9.2; iPad Pro 2nd Gen, iPadOS 16.2; iPhone 12 Pro, iOS 16.2; TV 4th Gen, tvOS 16.2; HomePods, audioOS 16.2 and Airport Express w/ Airplay 2

very simple. long press on watch screen. then swipe towards left. at the last you will find various option to add. you can add percentage. You can add by using watch faces in iphone and apply.