How to add pronunciation to “spoken content”?

I use the "speak selection" command that's part of "spoken content" under accessibility. I use this command to listen to my text books, however, it cannot pronounce Greek letters whatsoever (for example, 'gamma' is pronounced 'micro-velta' and the voice changes from male to female). I have a 2023 Apple M2 Pro and there's no option for "add pronunciation," which seems to have existed for previous mac versions.

Under "VoiceOver" there is an option to "add pronunciation," but things I add here does not apply for the "spoken content" command.

Any help would be appreciated! Thanks!