File Extension VSX File Format Visio Stencil XML File VSX stands for Visio Stencil XML File. This was last updated in March 2012 By Margaret Rouse Browse File Extensions Alphabetically: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # Ask a Question. Find an Answer. Ask your peers a question about this file extension. Ask a Question Need to open network diagram Visio 2007 AutoCAD to Visio?