I asked a comparable question some month before. But I get no answer. It seems to me that there is no way to import a GPX-file as a route. Although at the manual in the import/export section is written, that you can.
Within the import function there is a switch for importing the GPX-file as a path or not. I think, “not as a path” means, to import it as a route. But anyway if I select yes or not, always the file will be imported as a path 🙁
But it makes no sense, if you use such an imported path to start recording your own path. PE will record your way in addition (min & km) to the imported path. And the imported path has the same colour like your recorded path.
I think this function is buggy.