This is the problem with Manifest 3. Lots of extensions are effected.
Riz announced awhile back that he was leaving TiddlyWiki to spend more time with other software, or something like that. So unless he comes out of retirement, probably not much help from that quarter.
The 3 solutions that work really well (though actually I haven’t tested them under Manifest 3) are
You just keep a copy of TiddlyStow (TS) on your desktop, and open it whenever you want to open a TW. It even gives you a menu of the last 10 or so files that you have opened. The downside is that if you have any external files with relative paths, you won’t be able to see them. There are workarounds to that problem, possibly.
The TW5-browser-nativesaver (TBNS) uses a plugin. So the main complication is setting up your TW5 file initially. After that, there are a couple popup question boxes you have to answer in the affirmative every time you reload. Also you need to tell it to use the internal database of your browser, or it will ask you for a save destination every time you save. But once you have it working it understands relative paths, so it’s more natural that way.
The tool I mostly use now is rclone. You just download rclone from rclone.org. Go to the directory where you have put the rclone executable (typically rclone.exe on Windows). Give a command like:
./rclone.exe serve webdav ~/data/Wikis --addr :8080 --vfs-cache-mode full
Replace ~/data/Wikis
with the path to your folder of TW files.
Now you can navigate in your browser to 127.0.0.1:8080 and then click through to your TW file, double click and open. You can have as many TW files as you want open and they all share the same port number. Once you have your TW files up you can add them to your bookmarks so you can find them quickly next time.
This method should work with any modern browser no matter what. It doesn’t require a separate helpler file or a plugin. It does require you to start up the program whenever you reboot. I imagine it’s possible to automate this by putting a shortcut in the startup folder, but I’ve never done this to verify.
There’s also a way to open it up to your entire network, so if you’re on a wifi router you trust all your devices can access your files. It’s not something you would want to do in a coffee shop or an airport, but probably ok at home.