I have the same problem in Xcode. I'm currently using macOS Sonoma 14.5 with Xcode 15.4.
I have tested to follow Apple's guidelines but the fonts will not show up in the custom fonts list.
https://developer.apple.com/documentation/uikit/text_display_and_fonts/adding_a_custom_font_to_your_app
I have also tested to install the fonts to the Font Book but that did not solve the problem. Another thing that I tested (read in a forum) was to change the font color to trigger a custom font list update but that did not work either.
I can however get and use the fonts programmatically but that is not what I want to do in my project.
Any updates on this Apple? This thread is one year old and the bug is still there.