By "hibernate," do you mean "go dim or completely dark with inactivity?"

If so, then there are a couple of places I'd investigate.  One would be the screen's screensaver page, where you could try setting the brightness to the lowest level you can.

If you want it even darker (or completely dark) on idle, then the place to try would be in the PI-Star dashboard, configuration, expert settings, MMDVMHost area.  Look for the Nextion section for the IdleBrightness setting.  Completely dark is 0.  Just barely visible is 1.  I have mine set at 20 so it isn't overly bright to my eyes and tends to keep the heat down a bit.  I forget what the default is.

Regards,
Joe, WB3IHY