Just an idea, it might take a bit too much to implement… But I think it would be useful if the user could select a specific app to be used as an external editor, for when “view source editor” is chosen but an external editor is preferred. I know different editors have different methods for specifying a file to open, so it might be cumbersome and require “special handling” for certain editors, but I think it would be neat if possible.
In the meantime, as a short term alternative… if external editor is enabled and view source is selected, can the internal editor open and display the file in a “read only” mode? Sometimes I just want a quick look at a line or two.