Did you put them into a folder ?
The my_folder folder should show up as a new category under Tracklogs and would contain an entry called my_tracklog.gpx. It list everything that has a .gpx extension, so even if the tracklog has wrong internal structure, it should at least show up here.

I agree that this is quite confusing, there should be at least an "import tracklog dialog" so that users can easily select a tracklog and modRana would then copy it to the correct folder. And also support for some basic operations, like moving between categories, renaming, deleting, etc.