As someone who writes html only rarely (I'm more of a "backend" guy, and even use that term loosely.. most of my webdev experience dates back to the CGI days and often the html was spat out by Perl scripts) and usually in vim, I am pleased to know there is an in-built solution outside of me properly indenting or manually counting divs. Thanks for enlightening me.
A more common alternative to counting divs would be CSS classnames or (for unique elements on the page) IDs. You'd do `document.querySelector('.my-class')` to locate `<div class="my-class">` or similar, rather than using the fact that e.g. something is nested 3 divs inside <body>.
Even if this custom element trick didn't work, I don't see why one would need to count divs (at least if you control the markup, but if not then made-up tags aren't an option anyway). The article even mentions using class names as an option.
Sorry, I didn't mention class names because the article explicitly did and I assumed that my aversion to the extra typing would be presumed by a reader of my comment. My mistake.
So yeah, I guess what wasn't obvious from my statement of gratitude was that I appreciate knowing that there is a more concise way of keeping track - even without CSS styling. If I make up tags, they will just inherit default styling but to my eye I can be clear about where things are closed, and where to insert things later. I was talking about the manual editing (in vim, as I mentioned), rather than any dynamic query selectors. Make more sense?