Idk if this would work for older transitioners but long ago I saw a video of a young trans gal who managed to hide her adam's apple by basically tensing up the lower half of the jaw/throat and it would raise it to the point where it would look hidden. This also helps with maintaining a feminine pitch when speaking.
Anyways I did this prehrt a lot but it was difficult to hold for long periods of time but as I kept practicing it became easier and easier. After I started hrt and with my constant voice practice, the adam's apple looks like it shrunk. I can now relax it and it doesn't protrude at all and I can still speak in a male voice if I wanted to, which is like never
Also another tip is when you're practicing your voice, try to emulate like you're about to gargle. The way you tighten your voice box when you do that helps to keep the pitch in the right range and it doesn't sound like that super high falsetto mickey mouse voice. You should be able to stay relaxed.
