It’s a nice step forward, for sure! I personally would want to be able to pin it open, at the least. And for Rich Text Fields, I would prefer it to pop-out to the Left and not overlap contents (and also be pin-able), at least where width/screen space allow (I’m on a 4k monitor, plenty of room).
I also wonder if there is a way to better hint at what it is, make it more discoverable to whose who are less exploratory and don’t tend to just click on something that isn’t clearly identified. The on-hover pop-up text is helpful, and may be enough. Probably needs some time to see how people’s experience is with it.
Finally, for some reason I find the line length identifier for header size/level to be a less obvious/intuitive one than dot size. Is the longer line “bigger” (larger/higher level header, e.g. H1), or smaller (further indented, smaller/lower header, e.g. H3)? Turns out it is the former, but I wasn’t sure until I started clicking on them to see, and that’s not ideal. I think it should be immediately legible from the start, and the current design has some conflation with indentation as a representation of hierarchy IMO. I also feel that, even though it stays in the margin, it “feels” as though it is intruding a bit more on the text (and also reminds me of a ruler). If you prefer to keep the line length indicator, maybe combine it with a line weight/thickness.
Overall it’s pretty good as-is though, and it addresses the most important aspects of my feature request I think: it’s unobtrusive, floating/sticky, jump-click, collapsible, etc. 