Continuing the momentum of the rigidbody

So, I have a basic cube with a rigidbody on it. Then I created a grapple hook script that uses a line to represent that line between the point it hits and the player. I got it to the point where the player does go to the spot of the point that was hit, but if I stop the grapple mid air, it stops all moment of the cube and it just drops straight down to the platform below it. I want to be able to continue that momentum of the cube so it moves forward as it still drops.

Script:

 private void Movement()
 {
     float distance = Vector2.Distance(lineRen.GetPosition(1), hit.point);

     if (hitObject)
     {
         if (distance < 1)
         {
             Vector3 movePath = (transform.position - hit.point).normalized;

             RB.MovePosition(RB.position + movePath * Time.deltaTime * -pullStrength);
         }
     }
     else
     {

         RB.velocity = RB.velocity;
     }
 }
 private void SingleGrapple()
 {
     ray = Camera.main.ScreenPointToRay(Input.mousePosition);

     if (clickReady)
     {
         if ((Input.GetMouseButtonDown(0)))
         {
             if (Physics.Raycast(ray, out hit))
             {
                 lineRen.SetPosition(1, transform.position);
                 hitObject = true;
                 clickReady = false;
             }
         }
     }

     if (hitObject)
     {
         lineRen.SetPosition(0, transform.position);

         Vector3 newPos = Vector3.MoveTowards(lineRen.GetPosition(1), hit.point, Time.deltaTime * travelSpeed);

         lineRen.SetPosition(1, newPos);

         RB.useGravity = false;
     }
 }