Windows: no way to populate "Save as type" for FileSave dialogs?

[dweymouth]

As far as I can tell, there is currently no way to populate the "Save as type" dropdown when creating file save dialogs on Windows. This leads to a confusing user experience with setting a default save filename and an extension filter, since Windows hides filename extensions in the dialogs

[roffe]

Have you tried using .Filter?

// Filter adds a category of files to the types allowed by the dialog. Multiple
// calls to Filter are cumulative - any of the provided categories will be allowed.
// By default all files can be selected.
//
// The special extension '*' allows all files to be selected when the Filter is active.