Currently FG only allows one configuration for one joystick, however usually different aircraft have different controls that would be useful to map to the joystick, but can not be used on other aircraft (like changing the external view buttons to radar lock buttons on fighters). This could be done with changing the bindings each time using when flying a different aircraft, but that is definitely not an effective way to do it. That is why I would like to have a way to have multiple configurations that could be edited in the joystick configuration dialog under one joystick.
In addition to that, it would be also nice to have the custom configurations based on the default configuration unlike how currently editing from the default configuration creates a completely blank configuration. This would preserve settings that cannot be changed from the configuration dialog but are important for the joystick to function properly (like the 0.02 deadband on T16000M).