When you get a long list of compile errors, always go to the top, and look at the first error. As the rest are likely cascade events deriving from the first error.
In your particular case: Problems with // comments at the end lines, is however a general Arduino IDE problem, in combination with wrapper macros that are heavily used in Marlin.
The here and now solution is: use Platform.IO to compile.
And other option is, to remove the comments on those lines that give you errors. As it is mainly lines with pin numbers that cause this compile error.
Rather than remove the comments, you could also just send them to a new line.
Either choice will (here and now) get your compiler past this type of issue.
In your particular case: Problems with // comments at the end lines, is however a general Arduino IDE problem, in combination with wrapper macros that are heavily used in Marlin.
The here and now solution is: use Platform.IO to compile.
And other option is, to remove the comments on those lines that give you errors. As it is mainly lines with pin numbers that cause this compile error.
Rather than remove the comments, you could also just send them to a new line.
Either choice will (here and now) get your compiler past this type of issue.