Reinstalling or uninstalling an extension in Windows does not work currently.

This is because when DLL is loaded in Windows, we cannot unload it from PHP in order to free Windows' lock on the file. If you attempt to overwrite or uninstall the DLL in Windows, you will get an unhelpful/cryptic error like:

PHP Warning:  copy(C:\tools\php\ext\php_example_pie_extension.dll): Failed to
open stream: Resource temporarily unavailable in src\Installing\WindowsInstall.php on line 127

(this specific error is trying to re-install an ext that is already installed)

After some searching, it seems this is because the DLL is loaded and therefore cannot be "written" whilst loaded. One potential solution here is to relaunch PHP without the extension loaded. I believe Composer has a mechanism to reload without xdebug (for performance) so it may be possible to leverage that.