Access Steam features in the Windows WebView2, macOS WKWebView, and Linux CEF exporters. Requires r407.2+ for Windows, r417+ for macOS, and r412+ for Linux.
The File System manual entry does say Windows WebView2 is an exception and can write files directly without prompting - see the section "Accessing known folders". The new Linux CEF export option is also an exception (but is currently in beta - the manual will be updated when it's stable), and in future macOS WKWebView will be supported too.
Sure, I will study more about the FileSystem, Thanks