I know You are talking specifically about VSCode. So, most likely My comment may be irrelevant.

I happen to have a vídeo on having Elixir support on Sublime Texto 4.[1]

I Also do have a couple of videos on installing Erlang and Elixir on Debían. I am not sure if this can be reprocuced on a Mac.[2]

[1] https://youtu.be/LhDycf5G5RM?si=P_B9sqg3wSbsZ5mY

[2]https://youtu.be/pj8_UujqfN4?si=rFV7uEYY7QgKVFkv