Does the MobaTools Stepper 3 example do some of what you want?
It is unclear exactly what sort of synchronization or power you need. It is possible to wire a second stepper driver in parallel with the first to control a second stepper, and you can do a trick with the wiring to make it turn in the opposite direction.
If you need to move the steppers differently but still coordinated, it is also possible to do coordination in software.
For instance, here's a simulation of 32 coordinated steppers, all moving at different rates but in precise ratios to each other:
The motors, and the drivers you need to drive the motors would depend on the effort it takes to "spin a string".