How to Move Category position programmatically in Magento 2?

Move Category from one position to another using the move() method from the catalog module.

Function Definition from the interface Magento\Catalog\Api\CategoryManagementInterface,

/**
 * @param int $categoryId
 * @param int $parentId
 * @param int $afterId
 * @return bool
 * @throws \Magento\Framework\Exception\LocalizedException
 * @throws \Magento\Framework\Exception\NoSuchEntityException
 */
public function move($categoryId, $parentId, $afterId = null);

$categoryId indicates the Category Id to move,
$parentId indicates the Parent id to move your category,
$afterId default value is null. The parameter is used to move your category after a specific category, at that time you have to pass category id value for this argument.

When you have $afterId value is specific category id and not null value, you have to pass $parentId value will be 2(Default Category)

<?php
namespace Jesadiya\MoveCategory\Model;

use Exception;
use Magento\Catalog\Api\CategoryManagementInterface;

class MoveCategory
{
    /**
     * @var CategoryManagementInterface
     */
    private $categoryManagement;

    public function __construct(
        CategoryManagementInterface $categoryManagement
    ) {
        $this->categoryManagement = $categoryManagement;
    }

    /**
     * Move Category
     *
     * @return CategoryTreeInterface
     */
    public function moveCategory()
    {
        $isCategoryMoveSuccess = false;
        try {
            $categoryId = 40;
            $parentId = 2;
            $afterId = 20;
            $isCategoryMoveSuccess = $this->categoryManagement->move($categoryId, $parentId, $afterId);
        } catch (Exception $exception) {
            throw new Exception($exception->getMessage());
        }

        return $isCategoryMoveSuccess;
    }
}

Call the method from the PHP class to move the category position,

$isCategoryMove = $this->moveCategory();
echo "<pre>";    print_r($category->debug());

Output:
Boolean