@mbostock: A while back I forked your Notebook visualizer in an attempt to show imported cells:
I never ended up publishing it though because graphviz wasn’t up to the task of drawing the output (see the comments at the start of the notebook) and I never got round to finding a suitable replacement.
Also, the above fork works with runtime v1 JS modules so it no longer captures the way imports on observablehq.com work today. Spurred by your post, this weekend I’ve been playing around with parsing and processing v3 JS modules. I’ll edit a link into this post when I have something to share.
edit: I made a new thread.