Control stepper motor with low current and high current

Reducing the current of a stepper motor will not reduce its precision but it will reduce its "holding torque" feature. The holding torque is the ability of the stepper motor to keep its position when a torque is applied on its axis of rotation. If we take this one for example, it is not explicit but the max holding torque (4.8 Nm) is directly linked to the rated current per phase (6.0 A). I don't remember the exact equation linking the holding torque to the amperage but if you reduce the current, the holding torque will also decrease. If you intend to use a stepper motor not only to precisely move but also to stay in place when an external torque is applied (like holding a weight), you should take care of the current you are providing to the stepper motor.