H = visualize (G, VisPath => "/PATH/TO/TEMPLATE/")
This option is used internally to pass paths from one method to another. A savvy user would be able to use this option to create a personal template and pass the path for Visualize.m2 to use.
The source of this document is in /build/reproducible-path/macaulay2-1.25.06+ds/M2/Macaulay2/packages/Visualize.m2:1895:0.