I have small images of product at the side of large product image on a single product page.
The first three images are visible in the view and fourth one is not.
I want to make the fourth picture visible when user clicks the third image to make it active thumb.
Sorry, but the library we are using for the vertical carousel doesn’t have such feature. It can show the second slide (includes 3 images) only if you have at least 2 images to show (hidden). If you have only 1 image hidden it will not slide to the next 1 image. Unfortunately, we are not able to change this behavior in our theme.