A graphmz file extension is related to the GraphML graph file format. A graphmz file contains graph.
GRAPHMZ file extension - GrapML graph
What is graphmz file? How to open graphmz files?
File type specification:
The graphmz file extension is used for a graph file format (most likely compressed with ZIP)
GraphML is a comprehensive and easy-to-use file format for graphs. It consists of a language core to describe the structural properties of a graph and a flexible extension mechanism to add application-specific data.
This graphmz file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.