これで解決
defaults write com.microsoft.VSCode ApplePressAndHoldEnabled -bool false # For VS Code
defaults write com.microsoft.VSCodeInsiders ApplePressAndHoldEnabled -bool false # For VS Code Insider
https://github.com/VSCodeVim/Vim#faq
VSCode Insiders は正式リリース前のバージョンで、新機能がいち早く試せます