CaringCharge for Watch 4+

Controls charging of Apple Watch and will improve battery life with the outlet
which works with IFTTT Webhook.
In a word, this App is the semi automatic version of WatchOS standard function 'Optimized Battery Charging'. You can set as you like because of 'non full auto' settings (e.g. In 'Normal' and 'Cut at 80%' mode, the App stops charging at 80% without restarting to 100%).
The concept is almost equal to the iOS App 'CharingCharge'. Difference is the way to control the smart plug. This App uses IFTTT Webhook service instead of HomeKit. Take a look at the App's page in the App Store, please. And you can see how this App control charging.
https://apps.apple.com/us/app/caringcharge/id1505303275

'Caring' mode suspend charging when reached to the 80% capacity, afterwards restart at the time set. 'Normal' mode simply charge until reaching the capacity set. Difference is if the App restart charging.

'80% cut-off Normal Charge Mode' is very suitable for storing the devices as it will damage the battery when fully charged or empty.

Connect charger to the smart plug working with the IFTTT Webhook service, please. Lower current (not faster) charger is better in terms of battery damage.

The App can't work completely on background due to restriction of WatchOS. So this App can't control charging completely, but execute as ideal as possible.

'Optimized Battery Charging' is recommended to 'Off' not to conflict with this App.
(Settings -> Battery -> Battery Health -> )

Two 'Measure' mode is only for measuring the charge speed only and is different from the function with the same name in the iOS app "Caring Charge".