DragIndicatorController.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.EventSystems;

public class DragIndicatorController : MonoBehaviour
{
    private new Camera camera;
    private Vector2 startPos, endPos;

    private LineRenderer lr;

    // Start is called before the first frame update
    void Start()
    {
        camera = Camera.main;
        lr = gameObject.GetComponent<LineRenderer>();
        startPos = endPos = Vector2.zero;
        lr.positionCount = 2;
        lr.material.color = Color.black;
        lr.enabled = false;
    }

    // Update is called once per frame
    void Update()
    {
        if (!EventSystem.current.IsPointerOverGameObject())
        {
            if (Input.GetMouseButtonDown(0))
            {
                lr.enabled = true;
                startPos = camera.ScreenToWorldPoint(Input.mousePosition);
                lr.SetPosition(0, startPos);
            }
            if (Input.GetMouseButton(0))
            {
                endPos = camera.ScreenToWorldPoint(Input.mousePosition);
                lr.SetPosition(1, endPos);
            }
            if (Input.GetMouseButtonUp(0))
            {
                lr.enabled = false;
            }
        }
    }
}