This doesn’t 100% cover all these cases, but with the new Observable search, you can search for (public) notebooks that might import cells from your notebook. Like with Mike’s Safe Local Storage notebook, you can search:
mbostock/safe-local-storage -author:@mbostock
And the search results returns notebooks that mostly likely contain a cell with import {localStorage} from "@mbostock/safe-local-storage". It’s also possible that someone is importing the notebook with the notebook ID or the full url, so you might wanna change the search to cover that
Again, not 100%, someone with better observable search-fu might have a better query, but if I’m curious about who uses my notebooks, or I’m checking to see if a change in one of my public notebooks break something, it’s a good quick litmus test for that.