above will not compile.
this will:
struct Motor {
int stepPin;
int dirPin;
int direction;
int RPM;
bool run;
int steps;
} myMotors[4] = {
[0] = {13,14,15,16,false,0},
[1] = {23,14,15,16,false,0},
[2] = {33,14,15,16,false,0},
[3] = {43,14,15,16,false,0},
};