The documentation for
SystemDialogInput shows how to restrict the types of files shown.
...only shows Mathematica notebook files. This also works for other file extensions such as ".txt", ".html", etc., but doesn't work for other file types.
If I have a tab delimited file that with extension ".data" and try:
...the dialog box defaults to all files.
Is there a way to only show other "non-standard" file types?