Fieldset items ordering

[MMGFX]

I created fieldset to create list in my page. I want to sort items with simpy drag&drop. I can see handlers on the left but it doesn’t work. How can I order items by drag&drop method? Below is my code

            header.fieldsetFirst:
          type: fieldset
          title: First tramp items
          collapsed: true
          collapsible: true
          fields:
            header.custom.firstTrampItems:
              name: firstTrampItems
              type: list
              style: vertical
              label: First Tramp items
              fields:
                .item:
                  type: text
                  label: Item