New created scroll content overlaps last scroll content created

I use scroll Rect.

Each content contains a dropdown, three input fields, and a button.
Each content has a content size fitter and a horizontal layout group.

How do I make the newly created content automatically placed below the last content created?

When you add new stuff to a Scroll View Containers, it’ll always just write it over the top of whatever you called up previously. So it’s up to you to clean it out.

Before you populate your OperationListContainer again, call this method:

public void ClearContainer()
{
    foreach (Transform t in myAwesomeContainer)
    {
        Destroy(t.gameObject);
    }

}

You can even set it to a button so you can clear it out whenever you need to.

Just keep in mind it will wipe out everything in that container, so be careful!