Como eu resolvi: listar todas as extensões instaladas no Visual Studio Code

Só precisa de um comando:

code --list-extensions

Ou se estiver com a build Insiders:

code-insiders --list-extensions

Exemplo de output:

christian-kohler.path-intellisense
dbaeumer.vscode-eslint
eamodio.gitlens
EditorConfig.EditorConfig
esbenp.prettier-vscode
gluons.vscode-atom-javascript-snippet
joelday.docthis
joshpeng.sublime-babel-vscode
kisstkondoros.vscode-codemetrics
mrmlnc.vscode-stylefmt
ms-vscode.js-atom-grammar
msjsdiag.debugger-for-chrome
octref.vetur
shinnn.stylelint
WallabyJs.quokka-vscode
wix.vscode-import-cost