The Metal SM5 shader code cannot be viewed in the Editor for a Material. Prior to 4.20, only HLSL Code could be viewed. In 4.20, a number of additional shader options were added, and they all work with the exception of Metal SM5.
This only occurs on Mac. Metal SM5 shader code for iOS can be seen on Windows.
After compiling for a few seconds, no shader code is displayed in the window.
After compiling for a few seconds, the window displays the Metal SM5 shader code.
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-63324 in the post.