This left-most HTML table column in the columns settings table has no input. Instead, it is used to sort (drag and drop) the order of the HTML table rows (hence the dropdowns) as you wish. To perform a sort, hover your mouse on a row in this HTML table column, hold and drag it to your desired location.
Please note that sorting may invalidate the relationships and triggers between dropdowns. You will need to edit those settings if you sort your dropdowns. Otherwise, on save, the field will throw an error about invalid relationships and/or triggers. These are discussed in the next topic.