I want to share my final solution which works quite well. Maybe it can help someone else.
Summary: I used a trigger - instead of collision - in order to fully avoid any physical interaction between the objects and simulated the physical impact on the coin manually. This works better than initially expected ;-)

The setup for the coin game object (which shall receive the simulated physical impact) looks like this:

The coin_Master has a Collider with isTrigger = true and the Layer set to "Collectibles_noCollision"

The justCollider sub-object has just another collider with isTrigger = false and the Layer set to "Collectibles_DoCollision".

The layer collision matrix looks like this:

And this is the code which simulates the physical interaction. As you can see there are some parameters with which I finetuned the solution.

  
// The Collider of the coins has to be marked as "Is Trigger" 
private void OnTriggerEnter(Collider other)
{
    HandleTrigger(other);
}

private void HandleTrigger(Collider other)
  {
      if (other.CompareTag("Player"))
      {
          // Calculate an impulse, e.g., away from the player
          Vector3 adjustedPlayerPosition = other.transform.position + new Vector3(0, 0, -1);
          Vector3 direction = (transform.position - adjustedPlayerPosition).normalized;

          // Get current player speed
          Rigidbody playerRigidbody = other.GetComponent<Rigidbody>();
          float playerSpeed = playerRigidbody.linearVelocity.magnitude;
          float speedFactor = 0.18f; // Scaling factor to adjust the influence of player speed

          // Calculate the final impulse:
          // Here, the base impulse (impulseForce) is multiplied by the player's speed.
          // You can also add or weight both components (the base impulse and speed).
          Vector3 finalImpulse = direction * impulseForce * (1 + speedFactor * playerSpeed);

          // Define scaling factor for negative y-component
          float yScale = 0.2f; // Example: 20% of the original Y-force if downward
          // If the y-value is negative, weaken it -> avoid a too strong braking effect, if the player is (much) bigger than the target object (coin)
          if (finalImpulse.y < 0)
          {
              // Debug.Log($"LevelObject_Coin > OnTriggerEnter > CORRECTing y impulse - finalImpulse: {finalImpulse} finalImpulse.y: {finalImpulse.y} ");
              finalImpulse.y *= yScale;
          }

          Debug.Log($"LevelObject_Coin > OnTriggerEnter {gameObject.name} > playerSpeed: {playerSpeed} finalImpulse: " + finalImpulse + "> finalImpulse.magnitude: " + finalImpulse.magnitude);

          // Apply the impulse – using ForceMode.Impulse for an immediate effect
          coinRigidbody.AddForce(finalImpulse, ForceMode.Impulse);

          // Disable the trigger or collider object, so this logic is only executed once
          coinCollider.enabled = false;

      }
  }