Use the Unity Input System to drag an object by dynamically adding and removing event handlers.

Dragger.cs

// This example calls for an object to be designated for dragging
// by explicitly setting a Transform. That's enough to demonstrate
// the method. Real production code would need to use a Raycast to
// find the object to drag. It would be much more sensible in that
// setting to have the MoveStarted, MovePerformed, and MoveCanceled
// methods supplied to this code by the object being dragged. That
// would allow any kind of "dragging," such as turning a dial, or
// moving within limts. This video goes into that in detail:
//
// https://youtu.be/WjPDPyt3pBY

using UnityEngine;
using UnityEngine.InputSystem;

public class Dragger : MonoBehaviour
{
    public Transform dragObject;
    public float scale = 20;

    public InputAction moveAction;
    public InputAction dragAction;

    Mouse mouse;

    Vector2 startOffset;

    void Start()
    {
        mouse = Mouse.current;

        moveAction.Enable();
        dragAction.Enable();

        dragAction.started += DragStarted;
        dragAction.canceled += DragCanceled;

    }

    void DragStarted(InputAction.CallbackContext c)
    {
        Debug.Log("Drag Started");

        moveAction.started += MoveStarted;
        moveAction.performed += MovePerformed;
        moveAction.canceled += MoveCanceled;
    }

    void DragCanceled(InputAction.CallbackContext c)
    {
        Debug.Log("Drag Canceled");

        moveAction.started -= MoveStarted;
        moveAction.performed -= MovePerformed;
        moveAction.canceled -= MoveCanceled;
    }

    void MoveStarted(InputAction.CallbackContext c)
    {
        Debug.Log($"Started {mouse.delta.ReadValue()} {mouse.position.ReadValue()}");
        startOffset = mouse.delta.ReadValue();
    }

    void MovePerformed(InputAction.CallbackContext c)
    {
        Debug.Log($"Performed {mouse.delta.ReadValue()} {mouse.position.ReadValue()}");
        Vector2 totalOffset = mouse.delta.ReadValue() - startOffset;

        Vector3 position = dragObject.position;
        position.x = position.x + totalOffset.x / scale;
        position.y = position.y + totalOffset.y / scale;
        dragObject.position = position;
    }

    void MoveCanceled(InputAction.CallbackContext c)
    {
        Debug.Log($"Canceled {mouse.delta.ReadValue()} {mouse.position.ReadValue()}");
    }
}