We plan to implement customization for charging. It requires doing research/design work to come up with a sensible approach rather than simply what other operating systems are doing. There's a lot of evidence that providing control over the minimum capacity to begin charging and the maximum charge capacity would be useful for people who want to sacrifice a bit of short term battery life to preserve it better in the long term. Charge rate is already throttled based on capacity where it greatly slows down as it approaches 100%. it's also already throttled based on heat. We have most of the standard battery health features used on Pixels, just not the adaptive charging feature which guesses your schedule and slows down or limits charging in some cases.
A lot of people are passionate about this topic and there's conflicting information. GrapheneOS developers didn't participate in this discussion and none of it before this post is official info from the project. Current lack of non-standard features in this area doesn't mean we don't want to it, but we generally agree with the standard approach other than adaptive charging often not doing what people want/expect. Providing a bit more control over the standard approach rather than layering another on top may be exactly what's needed. Controlling how much it slows down based on heat, charge capacity, etc. along with controlling how high it goes is probably all we really need. Expecting people to manually set a scheduled time for charging over and over is unrealistic and conflicts with charging whenever you can.