I now have a release of an initial implementation, ready for people to play around with.
It works like the 2.7 version with headers on the side. The header width and pane width is configurable via the settings, and there is also a command to toggle it on and off (which you can configure a hotkey for).
Changing the active pane will scroll that pane into view. So now you can click on titles, or set up hotkeys to navigate between panes, and they will scroll into view.
I’ve also got the headers stacking up on the right as well as the left, so you can click on panes to the far right as well.
There’s still a lot of work to be done and more options to be added in the future. For now, it might be a bit funky with some themes that mess with headers (like Notation or Minimal) and will probably also have issues with themes that have Andy’s mode built into the CSS.