I see, so you make edits, the Javascript edits the html, therefore File -> Save Page will download an html file with your changes in it that you can open again.
I forget that File -> Save is even a thing for websites.
Note: The TiddlyWiki documentation explicitly advises that File -> Save Page does not work.
You have to click a save button in the app, and it will generate a valid copy. However, most users deploy some plugin or software which allows transparent auto-saving.
They never did, if anything it's the opposite in that I think there are now APIs that can make this possible.
With TiddlyWiki you had to essentially File -> Save As and save the HTML back over itself. There were other ways too but they were all workarounds to the issue that browsers don't allow direct access.
They did back around 2008. I used Wiki on a stick - see https://stickwiki.sourceforge.net/which was kind of neat) but after a few years, Chrome etc stopped letting it save itself.
TiddlyWiki can replicate itself. All users can freely edit any TiddlyWiki and save their changes to their filesystem. There's a few options for exports.
It is a common gotcha that new users will lose some of their work while they learn persistence.
