XmMainWindowSep3 returns the widget ID of the third Separator in the
MainWindow. The third Separator is located between the
message window and the widget above it.
This Separator is visible only when XmNshowSeparator is True.
NOTE: XmMainWindowSep3 is obsolete and exists for compatibility
with previous releases. Use XtNameToWidget instead. Pass
a MainWindow variable as the first argument to XtNameToWidget
and pass Separator3 as the second argument.
For a complete definition of MainWindow and its associated resources, see
Specifies the MainWindow widget ID