Geant4 visualization and UI drivers can be in Geant4 VMC enabled via dedicated CMake configuration options. See more details in Installing Geant4 VMC.
The G3-like functions for visualization defined in TVirtualMC are overcome with the interactive visualization capabilities of both Root and Geant4 geometry modellers, that’s why user is encouraged to use these modeller directly. User can set Geant4 visualization options using Geant4 visualization commands, as it is illustrated in the VMC examples in g4vis.in macro.