Not sure if this will help (or that it responds to the type of ‘hack’ you might be after), but in case:
In this post from awhile back, @mootari provided custom CSS to put cell names back into the left margins:
@-moz-document domain("observablehq.com") {
div[id][data-node-id]:before {
content: attr(id);
position: absolute;
right: calc(100% + 20px);
top: 5px;
pointer-events: none;
z-index: 1;
}
}
Regrettably it doesn’t seem to be working now 
If you can get it to do so, please share!
I lamented about this before on the forum, but I think it’s a shame that these labels aren’t immediately visible anymore on certain types of cells (like html and md cells… or maybe all tagged template literals).
Mike gives a clear explanation for the change, and of course, he the Observable team are pros, and I am in no place to question their technical judgement, but I think this comment merits a quote:
… And to extend this a bit more, for me it’s a bit of a challenge when I want to embed bits of a notebook with lots of little html cells that I have unpinned, and to figure out if I named them I have to click into each. Fortunately Jeremey’s Handy Embed Code Generator expedites this process for me rather substantially.
Alas! Even if these weren’t visible on some devices, there are other bits of the platform that I find really hard to see and interact with when not on a desktop (like comments)!