I'll second TiddlyWiki. I've used it for several years and became a fan early on.

These days you might run across some hiccups in getting it to work in your browser of choice. Over the years the browser vendors became less and less inclined to allow javascript and extensions attain local file editing permissions. That's pretty reasonable, but annoying.

A pretty decent alternative that I've been using for months, now, is an app called Tiddly Desktop. It's an NW.js-based app so it has no trouble accessing the local filesystems.