@von212 You issue is all about the code… Blynk would simply be a GUI, not the actual driving factor.
Another thing to consider is the type of motor you use. I made a slider prototype once using a stepper motor and HALL sensors & magnets for limit switches.
This is an older project., and a rover not a camera slider, but a motor is a motor… I don’t recall if I since implemented auto stop at connection loss, but this would be something to get you started with mixing motor controller commands and Blynk interface.
And a “shield” is just a fancy way of saying a “form fitting” module. A L298N based motor shield or standalone motor controller is the same technical thing.