Means of controlling the battery charge voltage limit on Bangle.js 2?

The Chargie seems very cool. Thanks for dropping that name, I had searched for something like that a few months ago without success. I use a Palm Phone with a 770mAh battery and that degraded to about half its tiny capacity in 2 years of use. Charging daily or currently twice a day and using 100%-0% every day will do that fast. The Bangle with its week long runtime will probably degrade more by age than by charging.
As for the Bangle, a workaround would be charging from a powerbank. Many of those cut off the charging when the current is low. The Bangle draws miniscule amounts of current at the end of charge so depending on the powerbank that might hit your target charge level on cut off. Some reviews check the minimal amount of current needed to keep the power on, that would be your charging cut off value ;).