There is only one file type that uses the .VTM extension:
Visual Tool Markup Language Document
File created in the Visual Took Markup Language (VTML) format; enables developers to extend a program's user interface with new components; often used for defining functions for code hinting, completion, and formatting; also used for creating new language tags.
VTM files are used by Adobe Dreamweaver, and are also used by older programs, which include Adobe ColdFusion Studio, Macromedia HomeSite, and JRun Studio.
Updated: November 12, 2018