I just found out that quarter tones aren't the only microtones. Now I'd like to experiment and write music with microtones. I'd like to know how to read and write with sagittal notation (or other notations) and learn about them.
This is is the official forum for Sagittal notation.
I assume "the chart" you refer to is the one on the front page of the link @awelotta shared (here). That's the Periodic Table of EDOs, and it's one of the most recent developments in Sagittal notation. Because it's so new (November of 2019) there is not much formal explanation about it yet. It's super cool and I think that's why it's being shown off front and center. As I'm sure you can tell, it contains a lot of information. And there's even more information that one can infer from it... if you have some background knowledge about microtonality. If you are just getting started with microtones and microtonal notation, it may not be the best place to start. (If you do really want to know more about that specific chart, though, you can read the forum thread where it was developed here)
When you have more specific questions about Sagittal, I recommend you should sign up for an account on the forum. I'm an active user there and I will be more than happy to help answer your questions.