Timimi is a Web Extension and executable for Firefox, Chrome and Chromium that allows it to save standalone TiddlyWiki files.
https://github.com/ibnishak/Timimi
This is an addon using native messaging, essentially handing over the contents to a webextension host (executable) which does the actual saving. Once installed, you can save the standalone TW from anywhere in your hard drive without any more interactions, like the original Tiddlyfox addon.