See #7035 & #3884

Persist an extension manifest file extensions.json that lists all extensions installed and other relevant data (whether they're disabled?), on launch the list could be checked and automatically install extensions. This would help enable:

• Roaming on Windows Revisit VS Code folder structure for app data, settings, extensions #3884
• More logically cache and config files on Linux, also Revisit VS Code folder structure for app data, settings, extensions #3884
• Allow extensions or external programs to sync extensions more easily

This is a soft dependency for #3884