Browser storage
Test Native Sandbox Memory IndexedDB Cache storage
Total
      getOriginPrivateDirectory(),
      getOriginPrivateDirectory(import('./adapters/sandbox.js'))
      getOriginPrivateDirectory(import('./adapters/memory.js'))
      getOriginPrivateDirectory(import('./adapters/indexeddb.js'))
      getOriginPrivateDirectory(import('./adapters/cache.js'))
    
Manual save & open file(s)/directory
Manual Testing
showDirectoryPicker({
  _preferPolyfill:
})
showOpenFilePicker({
  _preferPolyfill:
  multiple:
  excludeAcceptAllOption:
  types:
})
showSaveFilePicker({
  _preferPolyfill:
  _name:
  excludeAcceptAllOption:
  types:
})
Drag and drop

The DataTransfer are very similar to Blinks sandboxed filesystem. so it would be easy to just convert the event to a FileSystemDirectoryHandle and use the sandbox adapter on it.
elm.ondragover = evt => evt.preventDefault()
elm.ondrop = evt => {
  evt.preventDefault()
  getOriginPrivateDirectory(evt.dataTransfer)
}
Drop anywhere
on page