Work really nice on Windows 11. Really solve the multi-profile browser problem. But need some installing some .exe extension from github.

For those with FF 124.0 that broke this plugin. Here's how to fix this temporarily:

1. Hit Windows + R.
2. Put "%APPDATA%\nulldev\FirefoxProfileSwitcher\config\" inside the prompt, and hit "ok." This will open the configuration folder. The address should look like this:
C:\Users\[yourusername]\AppData\Roaming\nulldev\FirefoxProfileSwitcher\config
You should see avatar.json and profile-options.json
3. Right click anywhere inside the "config" folder, and create new text document. Name it "config.json".
4. Open config.json (with notepad) and paste the following text into config.json:
{"browser_binary": "C:\\Program Files\\Mozilla Firefox\\firefox.exe"}
5. Save.
6. Reopen FF.

credits to: olivrrstray