Hi @TiddlyTitch and @CodaCoder, I looked again at InnerWiki and DevTools and it wasn’t hard to find out how to use it with the InnerWiki iframe. I have no idea why I failed before. Using Brave now and might have used Edge in the earlier tests, but that shouldn’t make much of a difference, both being Chromium-based. They don’t have the iframe isolation button that Firefox seems to have, but e.g. the Sources panel presents the iframe sources separately and lets me set breakpoints and whatnot to aid in debugging.
Anyway, I’ll be using InnerWiki again for working on JavaScript modules from now on.