@darnz said in External Drivers for Nema 34 Steppers:

Could I make use of expansion plug pins for my XY and Z?

So useE2 for my X
Use E3 for my Y
And use E4 for my Z.

Yes, use the M584 command in config.g to specify which drivers your axis motors use.

Do you think I may have a problem with one pin feeding signal to upto4 drivers?

You might be able to drive 4 drivers from one expansion breakout board output. Or you could use E4 and E5 to drive 2 Z drivers each.