Install extensions via command line:

code --list-extensions
code --install-extension ms-vscode.cpptools
code --uninstall-extension ms-vscode.csharp

VS Code help for extension install

code -h

Extensions Management:
  --extensions-dir <dir>                                         Set the root path for extensions.
  --list-extensions                                              List the installed extensions.
  --show-versions                                                Show versions of installed extensions, when
                                                                 using --list-extension.
  --install-extension (<extension-id> | <extension-vsix-path>)   Installs an extension.
  --uninstall-extension (<extension-id> | <extension-vsix-path>) Uninstalls an extension.
  --enable-proposed-api <extension-id>                           Enables proposed API features for an extension.

And--force --install-extensionto update