If you mean uninstall, then you would do this through the same mechanism you do with another other software you would install on your computer. i.e. On Windows, via the Add/Remove Software control panel / settings section. Mac has some sort of software management section also.
If you mean how do you reset everything so that you can ensure that there are no corrupt settings, etc, then the simplest way is to remove the $HOME/.platformio directory (Windows: %userprofile%\.platformio, Mac/Linux: ~/.platformio), and restart VSCode, at which point the PlatformIO IDE extension will do a full reinstall of the platform, unless you uninstall the extension as well. There shouldn’t be any need to do anything to VSCode unless you’ve changed setting there. Not sure what the best mechanism to reset VSCode is - perhaps deleting the settings directory for it also would be sufficient?
It would be best to continue any troubleshooting efforts on the other thread you opened here :