At a previous company, we got to the point where we were considering making a Chrome extension to support an out-of-band workflow for our app. I, being in my 40s, suggested the prototype could just be a bookmarklet. All the younger devs were like "what's a bookmockler?" and I felt very old.
Almost as old as when I started singing The Wreck of the Edmund Fitzgerald when asked if I could name all the Great Lakes.
They're so simple that it's hard to believe they just work. I'm almost surprised that browser vendors haven't pushed the functionality out of existence just because, in favor of ever more complicated solutions.
Similarly, while prototyping an internal company wiki I made bookmarklets to fix some Sharepoint shenanigans and add features that otherwise would've required mucking about with extensions (tough when half the company was forced to use IE) or even worse, Sharepoint apps. The entire IT staff had a major WTF moment after explaining just how simple the whole thing was.
I made one to collapse all comments in a BitBucket PR page (just find each comment and nest it inside a <details> tag, with a <summary> containing the first line of the comment). It's widely used in PRs that deal with Atlantis/Terraform, because Atlantis leaves huge comments on PRs.
Almost as old as when I started singing The Wreck of the Edmund Fitzgerald when asked if I could name all the Great Lakes.