Some people mentioned that it was not obvious that you could move the camera, so I added arrow buttons in the menu to do it.
You can also use the keyboard shortcuts:
-A or Arrow left: Move camera to the left
-D or Arrow right: Move camera to the right
-Q: will place the camera on the first cart
-W: will place the camera on the cart that is in the middle
-E: will place the camera on the last cart
There's also an option in Settings -> Gameplay to sort carts based on the current client's order. Enable this option to place the carts that produce the wanted items for the current client in the first slots. This way you won't even have to move the camera to find the carts.