When adding an extruder to a printer profile, it would make more sense to duplicate the settings for the first extruder rather than loading default values, as most printers using multiple extruders are using identical extruders. The user could then change those settings, but this will mean that 99% of the time, the settings will already be correct and they won't have to go to the trouble of copying settings from the first extruder tab to configure a second, identical extruder.
Use last extruder's settings when adding new ones. #1997
Good idea, done!