File System Access API for Plugins

Is it possible to use the File System API in Figma Plugins?

For example running window.showDirectoryPicker() in the console works, but trying to run it in a plugin returns undefined, likely because it's in an iFrame.

I was checking the manifest settings to see if it’s possible to add permissions at that stage, but it doesn’t look like there are any relevant options.

Ability to use the File System API would be very useful for plugins that need to export documents to local disk at multiple points in time without requiring the user to select the same folder over and over again, and without the need for a sidecar desktop app to manage local files.