H = visualize (G, VisPath => "/PATH/TO/DIRECTORY/", Warning => false)
When using the option VisPath a warning is produced if files will be overwritten. Warning is used to squelch these warnings. The default value is true, meaning the warning will be displayed.
The source of this document is in /build/reproducible-path/macaulay2-1.25.06+ds/M2/Macaulay2/packages/Visualize.m2:2000:0.