any way to do this for a class that uses imports/exports?

Require is for asynchronous module definitions. For ES modules you’ll want to use dynamic import. You may also want to use a CDN such as Skypack. https://observablehq.com/@visnup/hello-skypack

thanks -- specifically our goal here is to use an ES class that is under regular development on github, without publishing it elsewhere (cdn or npm) on each change, and without copy/pasting it into observable each change

Try this: https://observablehq.com/@mbostock/import-from-github

that's much cleaner than what I was doing previously - thanks much