The subject of “larynx height” comes up again and again. A friend recently sent a student off to a solo festival and the judge wrote “keep your larynx down”. That is not helpful. Conscious placing of the larynx at a particular elevation in the throat causes problems.
Yes, you can quote Richard Miller, et al, to me and use all the caution words like “comfortably” and “relatively” and “somewhat”, but direct mechanical control that is not based in making a free, easy, efficient sound is bunk. If you try to fix one thing by direct control, you will mess up something else.
Good singers may train in ways that cause a larynx to descend, or to stabilize, or to tilt, or whatever the mechanical people are looking at these days, but these things come most successfully from concepts that are related to an expressive intention, a concept of sound, or a general physical attitude that informs the body un-self-consciously. In a highly able and healthy singer, the location of the larynx in the throat is a by-product of the way they sing. When asked about the height of the larynx, many great singers have disagreed about what it should do, or don’t even relate to the issue.
Rather than chasing after an effect, work on singing better generally. If someone with a small shrill voice and difficulties with range, endurance, and flexibility learns how to improve in all of those problem areas, the larynx will go where it needs to, and usually that position will be lower than before. But if it isn’t, so what? Increasing ability, ease, and richness of sound are the prize.