The XCMD is called “StdFile” and takes a single parameter: the path to the volume or folder where the Standard File Package’s Open and Save dialog boxes should be positioned.
For instance:
StdFile("HD:Telecom:")
The command will beep if an error is encountered, and take no further action.
HyperCard seems to have the habit of resetting Standard FileΓÇÖs positioning in its idle handler, so itΓÇÖs a good idea to call this XCMD just before you need it.