Motor names are AMotor, BMotor and CMotor you need to define. That is actually all needed to have them.
For what are they needed? Often it is better to not have them and just switch E motor with that motor. Every extra motor adds code for stepping etc so motions get reduced max. speed from this. If you need them all to move same time that is the way to go. But e.g. for small adjustments or clearing plate you would sore them as E motor use function and restore e motor. Of course then requires own special gcodes to make sense of it.
You did not add one of the motor definition RAyWB showed you in configuration_io.h so AMotor is not defined causing the errors. They get defined same as x,y z motor but you need to add them.
Comments
Motor names are AMotor, BMotor and CMotor you need to define.
That is actually all needed to have them.
For what are they needed? Often it is better to not have them and just switch E motor with that motor. Every extra motor adds code for stepping etc so motions get reduced max. speed from this. If you need them all to move same time that is the way to go. But e.g. for small adjustments or clearing plate you would sore them as E motor use function and restore e motor. Of course then requires own special gcodes to make sense of it.