懸念事項だったローカルファイルシステムへのファイル保存について、
今後の Edge Browser では何か進展が有るらしい。

Native file system access
Up until now websites were not allowed to save files in a specific location on the user device.
This meant that online photo editors required users to upload the photo they wanted to edit and then download it to their device, while a native one would have just given the option to replace the existing one.
Starting from Edge 86 (version 83 is the latest one at the time of writing) developers will be able to replace all files the user selects in a session, thus enabling productivity apps on the web to even more useful.