Remote sensing workflows generally separate data manipulation and visualization. GPT is primarily a data manipulation tool. You can use ESA SNAP snappy to reproduce visualizations done using the GUI. In the past I have done that for batch processing workflows involving 100’s of images because I had NASA NetCDF4-CF data that was not yet supported by the GIS packages available at the time.
See: Export Bands as Images
GIS packages have a much wider user and developer base than ESA SNAP and put more emphasis on visualization, so may now be a more effective tool for visualization.