There no posibility to make movemebts where starting/ending RPM is not zero.
For example moves like:

Proposed in BasicStepperDriver to have method like:
void move(long steps, float startRPM, float endRPM);
or
void move(long steps, float endRPM); // end remember last/startRPM = endRPM
For more motors:
void move(long steps1, long steps2, float endRPM1, float endRPM2);
It will open possibility to make constructions/chains like:
void move(steps_to_x1, steps_to_y1, -1, 4);
void move(steps_to_x2, steps_to_y2, 4, 1);
void move(steps_to_x3, steps_to_y3, 0, 0);
Or there is another idea how to make that moves?