I'm not 100% sure if this is a bug or it's a feature (of lack thereof) but it goes like this:
On regular fiddler, a great thing to do is to simply copy a raw request to the raw composer, change a param and re-issue it... Fiddler everywhere does not allow that! I have to write headers on a tab and the body on another and yet, there's a "Raw" tab.
The Raw tab unfortunately is not editable (read-only)... I believe that it should be editable