Can I set a specific drive (e.g,"D:\") as a default directory for showOpenFilePicker?

We have a Java (JSP) application and I want (well, the client) wants when they save a file from the system, the file to be downloaded automatically by default in the USB drive. Also the same for when they are uploading any files to the system.

I know that this is not possible due to security reasons but I recently saw about this File System Access API and I am trying to understand what is possible.

Well, apparently for Downloading we can use

async function fileOpen() {
            const fileHandle = await window.showOpenFilePicker({
                startIn: 'documents'
            });
        }

but in the startIn property whenever I try setting D:\ or anything other than the WellKnownDirectories I get the error:

TypeError: Failed to execute 'showOpenFilePicker' on 'Window': Failed to read the 'startIn' property from 'FilePickerOptions': The provided value 'D:\' is not a valid enum value of type WellKnownDirectory.

So is something like that possible? What about when uploading a file? The file picker that opens from the <input type=file> doesn't support setting any value for the default directory.

Keep in mind the this is a controlled environment and the existence of the D: drive is ensured

Is there maybe any other way, other than JavaScript?

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