Gibbs-White is the heartbeat of this Forest side and therefore the hardest to replace. Elanga has proven himself to be an excellent signing for Forest - it was a privilege to watch him at Ipswich last season when he was largely unplayable.
However, I'd argue that fast, direct wide players who can finish are more common than those like Morgan who have something else about them. Whether you can procure one is another thing.
Out of the current crop, I'd be more disappointed to lose Morgan, Murillo and Anderson than Elanga. And I really like Elanga. As others have said, buy-low-sell-at-top-of-price-point is the only way provincial clubs survive in the Premier League.