That might not be difficult to do it yourself. Modus themes for example have code mappings, with a different coloration for code literals. In that file [1] for example, bg-main has the hex value of #000000, total black. If you want some part of the code to disappear, make it the same value. You could make builtins or constants #000000, and they will not be visible in the source file.

You can create different themes, like a comment theme, in which every part of the code is invisible (i.e. hex value black) except for the part you want visible, comments in that case. Then when you want everything visible again, you toggle the loaded theme.

I don't know if i will create such themes myself, my github account is on github/pramatias. I may upload something in the future, or may not.

[1]https://gitlab.com/protesilaos/modus-themes/-/blob/main/modu...