I don't know who I'm saying this for, but when one is drawing characters with cleft lip and/or palate, it is important to recognise that clefts go through bone as well as soft tissue. The reason why I'm saying this is because a lot of people just draw a normal face and then draw a line through the lip and put a gap between two teeth.
Because people with clefts have missing bone, the topology of the face is completely different to a regularly formed person's. This still applies to repaired clefts, to what extent depends on the original severity of the cleft and the success of the surgeries + orthodontics.
(I am going to use the word "cleft" by itself several times for the sake of brevity, please know I am referring to maxillofacial clefts every time. Clefts can occur outside of the maxilla, where they are known as craniofacial clefts, I will not be covering those right now.)
I find diagrams like this to be misleading, as they present the cleft like a thin "cut" in an otherwise fully formed head.
This is a more accurate visualisation of the condition, a cleft is more like a "gap" or "chasm". Tissue, both soft and hard, that would've been present in this gap is missing completely. That's skin, bone, muscle, teeth, and everything else.
People with clefts will often have a bone taken from usually the hip to be added to the upper jaw, to substitute for the absent material. People with clefts are also often missing adult teeth. Cleft repairs take a very long time, and that's under accessible healthcare of relatively high quality. The missing bone in the upper jaw causes most with maxillofacial clefts to have underbites, because the upper jaw is too short. Underbite correction is often the very last major surgery to be carried out. It is often done in the early twenties, because bones have stopped growing in length by that point in most people's lives. It is important to pay attention to the age of your character with a cleft. I don't expect you to have planned out an entire medical history, but the structure of a face with a maxillofacial cleft changes dramatically throughout early life. I think the underbite is the biggest thing I want to see more in people's cleft characters; remember the underbite caused by a cleft is due to a short upper jaw and NOT a long lower jaw.
For unilateral clefts, the nostril on the side of the cleft is smaller than the other, unless the cleft stops a while before reaching the nose. The cleft-side nostril also often has compromised breathing ability, causing many with clefts to rely on breathing through the mouth instead. People who are still going through treatment can have a fistula connecting the inside of the mouth and the nasal cavity. This fistula causes trouble with eating and drinking, as material passes into the nose and food can clog the fistula up. On the bright side, it can allow for the very cool party trick of being able to drink through the nose or eject fluids through the nose from the mouth. The deformed shape of the mouth affects pronunciation as well, since the jaws don't align as they should, people with clefts have to "cheat" to perform certain sounds. The voice also often sounds nasally because of increased airflow into the nose.
Even though the clefts are maxillofacial, effects can extend to the ears. People with clefts often get frequent ear infections especially as children, some have a flattened ear canal on the side of the cleft, and some have impaired hearing and may require hearing aids.
So I kind of forgot what the point of this was, but I just often see clefts treated by artists without them as a superficial detail that you can plaster onto a character's face with no structural changes. It is important to consider the underlying bone structure and how that affects the facial surface, and if the character is undergoing repairs how far along they are.